Even if it started out as an autumn festival, you've got to see what it's become today. For me that's enough to not celebrate it at all.
I've done research on it myself, not sure how you would sort out what is truth and what isn't because my information came from some pretty decent resources. It was awhile back, so I'd have to go search it out again and I really don't have the time to do that right now.
What halloween has become today is a fairly recent development in terms of history.
But if we are going to go with that argument, you'd also have to give up the rainbow as a symbol because it has become a symbol of evil and deception.
I don't think that we should give up things because the world has corrupted them, or has their own corrupted version of them.
As to what is true and what isn't. The first step is to look at the historical sources that are available. When someone tells you something about Halloween, try and find out what their source is for that information. Is the information available from historical sources?
Knowledge of history doesn't just appear. It is transmitted down through time. That means there is always a trail to follow if information is legitimate. If you can't find a source, or a trail, then in all likelihood the information is not ligetimate.
Further, in our day and age, so much information is accessible over the web, you can literally check historical sources and track academic sources on almost anything. Almost any major historical source document can be found online, and on top of that there are literally thousands upon thousands of secondary sources from objective sources talking about what is known on any given topic.
some common examples..
The word Samhain is often alleged to be the name of the celtic god of the dead (ie satan) to whom sacrifices were offered on Samhain (Halloween).
In fact, there is no known celtic god with the name samhain. The closest name among celtic legend is a minor hero named Saman, who has no connection to the dead or the underworld.
The word Samhain actually, most likely, is a derivation fo the compound word meaning "end of summer".
It is often stated that on Halloween the druids would go around to each house demanding tribute and if the tribute was not forth coming they would instead take a person from the house to sacrifice (this is supposedly the origin of "trick or treat")
In actual fact there is no historical record of human sacrifices being ascociated with Samhain, and there isn't even concrete evidence that the celts practiced human sacrifice. The commonly cited example from the Roman sources of burning prisoners of war alive in wicker cages is thought by many to actually have been a form of capitol punishment, not a form of ritual sacrifice.
It is commonly stated that samhain was a time of fear and trepidation when the people were terrified by spirits and ghosts roaming abroad.
In actual fact, the celt believed that times of transition were spiritually powerful. The transition from day to night at dusk, from night to day at dawn, from summer into winter at Samhain and from winter into summer at Beltain. The celts believed that at such times the veil between the spirit world and our world was "thin" and it was easier for spirits to cross over.
This, however, was not viewed as a time of fright, and terror. On the night of Samhain, it was believed that the spirits of a person's family (both those from the past and those from the future, yet to be born) could come to visit and basically check up on their relatives.
This was followed by a feast the next night called the feast of the dead, when all of the people would celebrate their ancestry and remember the great deeds of their family and tribe by telling the stories of their people etc.
This was actually a time of hope and drawing together in the face of on comming winter. Reminding each other that they all belonged to a family community that had survived for centuries and would continue beyond their own life times.
There are obviously pagan elements involved there, because the people were pagan and religion seeps into everything... we have only forgotten that because the prevailing religion of our day is secular humanism which presents the illusion that it is not religious.
When the people became Christian, those traditions changed over time as their Christian beliefs impacted their traditions. Rather than believing that their ancestors, and their descendants were able to visit them on that day, they used that day to remember that in Christ we are always in the company of a great host of saints.
I am not saying that everyone should go trick or treating (though I like candy and costumes more than most) but I think we should reclaim the heretige of the day and use it for what was and is a very worthy purpose.
One of the greatest problems in our society today is the disconnection people feel from others, from friends, family, community. We need to remember that we are part of something greater and we are members of a community.