Atheists how can you justify homosexuality?

"Love is Love" how many times have you heard this diatribe? NO Animal is the entire animal kingdom would even think about having gay sex, because the whole point of living is to breed, Homosexuality does not promote this, it makes it go back.. Lets go to logic class for all yall. 10 Dodo's are on a island, 5 are girls, 5 are guys, now if every single one of these birds were gay, then their species would die out. If only 1 of each gender was straight then breeding would be slow, and thus they have a higher increse as a species to die out. Love is only a chemical imbalance, it does not really exist, we just think it does except God's love, so technically you're "love is love" argument is flawed.

Additional Details
Yes, and every animal that does engage in homosexuality is endangered.