Most gay people, like most people, can take a joke and I at least have no problem laughing at gay related humour presented on television. I don't have particular problem with the colloquial use of the term gay or fag, even though it can be frustrating, it isn't what I would call prejudice or hate.
The worst thing you can say to a gay, asexual or trans person is that they chose to feel that way, that they chose to be gay or trans or whatever.
It is as offensive as saying a woman isn't as capable as a man, or a black person can never be as smart as a white person. It is suggesting gay people are somehow weird or crazy for choosing to be gay in a country that does not accept gay people for who they are. To choose to be gay in Saudi Arabia, Iran, Russia, North Korea, the South of the USA or Uganda would make you crazy, you'd have to be insane to choose to be gay when you know you're life as it risk for doing so, the threat of torture and attack.
It illustrates not only the belief that gay people are somehow weird, strange or unnatural, but demonstrates a great ignorance. This claim that being gay is a choice is not substantiated with evidence, the religious right, the conservatives, the fanatics and bigots alike claim homosexuality or transsexualism is a choice and as usual this claim goes unsubstantiated. Well science as always is prepared to look into this and have researched specifically the XQ28 chromosome, whilst not the only gene related to homosexuality in men it has been a great milestone in research. Scientists may not be set that it is entirely genetic, though have clearly explained the role of genetics, even as research goes and homosexuality in women is researched too. To say it is a choose, without evidence, is hateful and ignorant of the science, even though the science isn't as rigorous as other research, I for one trust a scientist more than a religious quack or hateful bigot. Science a side just ask yourself when you chose to be straight, "you know what I've decided I really like vagina after much deliberation and argument." Don't remember ever saying that?
It is like racism, like sexism, like ableism. A view that they are somehow separate or lesser, because they are not like yourself and you allow your own misconceptions and ignorance to support your view of that group.
I for one happy to be on the side of science, the side of humanists, Quakers, good Christians and good Muslims, good people, people who use their reason.
EDIT 17/04/2015: After a discussion with RandZul'Zorander I have changed my mind and approach to this, Rand is right to point out that ""it doesn't matter if it was a choice, there still is no reason to treat homosexuals with prejudice or discrimination."" I agreed with this at the time, however my line of thinking an adamant and unscientific one, I was aggressively suggesting that the belief that being gay is a choice amongst gay people is wrong, which I had no evidence to support. Though I would like to note a correlation between level of education and a belief in the genetic explanation for homosexuality. Though I agree with Rand that the research into why homosexuality exists needs to continue and absolute statements and being overly adamant is not appropriate nor reasonable. I would like to thank Rand for being more reasonable than I, and taking the time to talk to me.
If you believe being gay is a choice full stop, you are simply wrong, and if you like me say that those who claim to 'choose to be gay' are wrong then you had better have the evidence to support your claim. In the end your opinion is irrelevant, the scientific, verifiable and peer-reviewed evidence does not suggest it is a choice, it points to genetic and environmental factors and the research carries on. A commentor suggested I am not a reliable source, this person quite frankly is a bit stupid on this, as I am not a source and never claimed to be, this is purely an opinion piece. I do however point to a peer-reviewed paper later on in this thread.
Any reasonable person would trust the scientists more so than the myself or the far-right religious.