Whoa, when did I actually even mention the word sin? I'm going to assume you're a bit religious. What dictionary are you reading? Because after a quick google search this is what I got.
The belief that homosexuality is immoral is normally religiously motivated so its safe to assume that the word sin is appropriate for such contexts. I'm an atheist however.
Merriam-Webster as well as a few others. I'd provide links but website addresses aren't appearing in my browser for some reason.
Murder is a fact of life too when you consider the fact that people with various mental disorders are highly likely to commit it, the idea that just because something occurs naturally it has to exist outside of morality is nonsensical. I will say it again just to be safe, I don't think homosexuality is immoral. However whether or not you find something to be moral or immoral is not a matter of education (unless you count brainwashing), such thinking is only arrogant.
The very, very important thing here is that homosexual is something you ARE. You can't choose it. Just like you can't choose to be black, or white, or left-handed.
Murder is something you DO. It's a choice.
Nobody said "homosexuality is an opinion" in this thread.
Michael Lee said that believing homosexuality is good or bad is an opinion. And I don't want to make assumptions, but his comments seem to imply that he doesn't think it's "sooo bad to love someone of the same gender."