"Invalid. Or we should go back to the renaissance time where a marriage can be disbanded for remaining childless. "
Invalid? That's rather technical language for someone who just failed to discriminate between form and coincidence! ZING!
"The only valid reason for marriage is love. If two people love eachother they should be able to get married. All the rest is bullshit."
So long as the state is doling out tax benefits, I don't see what's wrong with them doing it to reward the productive endeavor of heterosexual marriage. Heterosexual marriage servers a function that homosexual unions do not.
"Your statement alone places you in one camp already. Your definition of "family" is very narrow. You even forgot about lesbian couples, but they seem to be forgot a lot in these discussions."
Lesbians are covered under the term "gay." I heard they like sexual partners of the same gender. That's still the definition for gay, right?
My definition of "family" is the same one that's been used for thousands of years. Are you taking issue with biology and nature? I didn't design sexual reproduction or the natural structure of society (again, for thousands of years) being based on that of the "narrow"ly defined family.
"A same-sex couple is able to form a firm base for kids though, a position well-proved by modern psychologic research."
Yeah, except for that pesky evidence to the contrary. You're quick to claim "proved" for something not remotely conclusive.
"Lesbian couples can conceive them on their own...."
That's just wrong. I can see why your claims on the science were similarly factually inaccurate. 
All of you guys like watching and reading about animals [reproducing] way too much. I'm not judging your sexuality, I'm just suggesting that maybe professionals could help you achieve balance in your lives. Whatever that is. Weirdos. 
"You have no choice in those distinctions, Einstein, yet you actively choose to deny a certain group the same as others by naming it differently."
I think nature denied them the ability to procreate, but I'll have to look into your theory that it was Einstein's call.
"The will to deny them that makes all the difference. It ultimatly shows you don't approve of it."
Damn you nature, you homophobic, judgemental bigot! Gay people want to create children and form families too! How dare you deny them their right!
" It says: "hey, we disapprove of you and your lifestyle, but we have to remain tolerant towards you". In a way it's the same as the segregation rules before Rosa Parks: You're all on the same bus, but a minority has to sit in an area that's reserved for its them."
Except that black people can do anything white people can do. And homosexuals can't do anything, like procreate, that heterosexuals can. And, as it turns out, procreation is kinda important to society.
I'm for government not being involved in marriage, but the claim that homosexual unions perform the same function in society is just false.
[I wish I could obey forum rules]