Well ... he was born that way. [/s]
They use that argument a lot. But it’s a totally bogus argument.
There are many savory predilictions that a lot of people are born with (pedophiles, arsonists, etc) that society doesn’t put up with.
I suppose they would come back with “but homosexuals don’t harm anybody”. Well we’ll see - perhaps its the whole society that gets damaged. We have a good test case underway between the US and Russia.