OK, space madness:
Jesus had no reason to bring up homosexuality because the Jews already knew it was against God's law.
First, that could be the reason, but then Jesus discussed many other topics that were part of the Mosaic Law. He considered they were important issues (read Matthew 5) even though the "Jews already knew" those issues. For example Leviticus 19:17, commands,
"You must not hate your brother in your heart."
So the Jewish hearers of Jesus teachings already knew that, but he still discussed the issue
Does his failure to mention male to male sex, (even though Palestine was under Roman occupation) mean that he did not consider male/male sex an important issue?
Second, in your brief argument you state that:
"the Jews already knew it was against God's law."
I presume your referring to the Leviticus, "gay-bashing" texts?
Leviticus 18:22 states:
"And you must not lie down with a male the same as you lie down with a woman. It is a detestable thing."
In reality, a man can't have sex with another man, " the same as you lie down with a woman."
I'm sure you've noticed that males lack a vagina. So the text is usually interpreted to be a prohibition on anal sex. Do you agree?
If you do, may I ask whether you consider it a sin when heterosexuals engage in anal sex?