Huh? Where did you get that impression? It doesn't say anything about prohibiting anyone with sexual inclinations, homosexual or otherwise.
What it says is this:
It is talking about someone who is ACTIVELY engaging in sexual activity *outside Holy Matrimony*. It isn't talking against someone having a same-sex orientation. And we know this by what it says next:
Therefore, in context, it is saying that if someone WAS FORMERLLY sexually ACTIVE at one time, and then were able to overcome this activity for a period of time THEN they would be considered for the priesthood since they will have demonstrated that they are now masters over their own urges. And sometimes our sexual urges are "deeply rooted...tendencies" which MUST be overcome if one is to be celbate.
Now...as to the question about straight seminarians...OF COURSE they too are called to celibacy and they too must master their own urges. The reason why this document had to be issued is in answer to the sex scandal which, like it or not, DID involve a significant amount of homosexual activity on the part of some gay priests. This move is long overdue, IMHO. This doesn't entail a double standard as straight men are called to the same level of celibacy as gay men.
God's Peace,
NewMan