I think the "parents will love you no matter what" line is actually pretty accurate. They haven't given their blood, sweat and tears to raise you for I don't know how long only to cast you aside because you don't like girls.
To give you an example, I was somewhat terrified of coming out to my mother on account of the fact she and her family had some religious leanings. Whilst my mother over a number of years slowly turned away from religion for a number of reasons, the one thing she always believed in was that homosexuality was wrong and wasn't "natural". And despite some initial shock and the typical "well I want you to get an AIDS test" she is fine with it now. She accepts that I am still her son and that nothing about my personality has changed - the person she has come to love is still here, just she won't be getting any grandkids out of me.
