The idea here is that some people (actually, a large number) have done nothing more than try to live their lives and get murdered or beaten for it -- there was no dispute and nothing they could have really been differently. The murder or beating happened solely because of who they are.
I don't think it was merely because they were gay, but largely because of the historical context in which homosexuality was conflated with pedophilia, communism "mind pollution", among some things. There was a large historic context of both ignorance and scapegoating of societal problems of various minority groups.
So, them being gay wasn't the issue as much as people were made believe that "gay" meant something else. The reason why in today's society homosexuality is normalized is precisely because those cultural myths were gradually and systematically were shown false.
Pedophilia is not the same thing as homosexuality, so there isn't reasons to make educational films like "Boys beware" and call the offenders homosexuals. Likewise, yes, private homosexuals were blackmailed by Communists into becoming spies, but it doesn't make all homosexuals Communists, etc, etc, etc.
In your examples, this isn't the case. In those examples, there was a dispute. The dispute may have been partially because of this identifiable trait but there was more going on other than just the trait. In the top example, the murderer did not just kill anyone that disagreed politically with him, he killed the man that he had a long running feud with -- the man's political identity is not the primary reason he was murdered. OTOH, for most protected classes, there tends to be a clear history where people have been discriminated against, and not being able to live their lives freely, solely because of some "class" (race, religion, sexuality, ethnic origin, etc.) that they belong to.
That's a point that abstracts the "middle of the dispute" from the "beginning of a dispute". Virtually all of the disputes begin with one group of people doing something, and the other group of people disputing the validity of that action of idea by bothering them. Thus, I don't really see that as a viable distinction.
So based on what I stated above, the reason homosexuals (and the other protected classes) deserve protection is because they were barred, in many, many instances, of being able to fully participate in society. Just one good example is the various "gay ghettos" you find in many large cities today. Gays were prohibited from buying or renting in most areas of the city, the only housing they could find were in some of the poorest areas of the city. Further pushing them into this ghetto was the fact that they could often be told they weren't welcome at many stores in the better areas -- so that would further push them to move to the ghetto, where their were "gay-friendly" stores.
Again, the only reason they can be barred from doing anything is if they are openly homosexual (which few people were) , if they are labelled as such in close-knit community, or if they have a criminal record in broader context of community (like sexual offenders are today). Otherwise, how can you tell apart a homosexual walking into a store? Especially if they are not openly homosexual.
These issues were complex in the past because of generic "mental illness" category in which a lot of things were thrown together indiscriminately (yes, that last word is important). Thus, there were a lot of pedophiles who were "homosexuals" who lived among homosexuals. There was a broader societal confusion on this issue, even among people who were generically labeled homosexuals and thus believed it to be an adequate label.
But, that's besides the point, because below is the main reason why it's problematic.
In this context, you'd have to justify connecting setting X to setting Y. Setting X is beating and murder, and setting Y is baking a cake for a wedding. In this context you'd have to consistently show that because X is wrong, therefore Y is also wrong in context of the "floodgate principle", meaning that if we are going to make up universal rules for people to live by, these would need to be consistently applied to various categories of mistreated people, if you are going to imply that because X then Y. That's the only reason I brought up this issue.
Otherwise, we are talking about two different settings - murder and beating is clearly wrong, and refusing to sell the cake is nowhere near or related to this issue, and you'd have to show how it's wrong apart from appealing to murder and beating.
Now, I'll agree, being "murdered" isn't "the" reason, but it is a part of it. Again, you had people who would sit outside of bars where gays were known to hangout, then they'd beat up or murder individuals after they came out of the bar (not wanting to take on groups that came out). There was no dispute, there was no disagreement, just that the person was suspected to be gay and was beaten or murdered.
Again, we should protect people against being beaten and murdered. I totally vote YES for that. But, that's not what you are arguing against in context of equality of rights.
All of us shouldn't be murdering each other, or be murdered by someone, right?
You can argue that no one should refuse to bake cakes for anyone... and I'll be the first one knocking on your door to prove that point wrong.
You can then say, but I don't bake cakes for living, but that's the point. You can't consistently transfer "Because no-one should be murdered" and then argue "This special category was beaten and murdered, and refused hosing and sales more than everyone, therefore no one should do that". You are mixing the settings and arguments.
I agree that murder is always wrong no matter who we are murdering or the reasons we have for murder. I disagree that refusing someone to sell something is always wrong no matter who we are selling to or the reason we have for refusal. Thus, you can't mix the two claims and throw these in the same category of claims as people did, and perhaps still do with homosexuality.
Basically, these protections were designed and are kept in place to ensure all citizens can participate fully in society -- they can live their lives as they chose without having to worry about whether an area will be "friendly" to their "kind" (i.e. not face discrimination, or worse).
OK, now you are switching the context from "beating and murder" to "friendly and kind". There's a vast in-between gap with these concepts.
Likewise, you are confused as to what's Government job should be. Government job is to protect against immoral extremes.
It's not there to enforce ideals. If someone is crabby hermit by nature of their existence, it's not government's job to force them to be a polite socialite.
Likewise no one owes anyone "the full participation in society". I know someone who is extremely shy and insecure with the world because of restrictions, expectations of him that were placed by his parents. As a result, he never dated a woman and is terrified of failure or rejection, and is afraid of job interviews, and the guy is 40. As a result of this psychological abuse by parents, he is also unable to fully participate in society... more so than many homosexuals today.
There are plentiful cases like that, and it's not up to the government to resolve these cases.
