No, I don't expect you to prove a negative. The presumption is, after millenia of humans living together in groups, I might add, that homosexuality is wrong, bad and an antithesis to material reality. You are trying to overcome that presumption when the evidence to support that presumption is in everybody's face every minute of every day.
The extraordinary claim is that homosexuality is consistant and harmonous with material reality as it applies to creatures, and equivalent to heterosexuality, which is the paradign of that material reality.
The burden is on you. 