I like to think I keep my cool in arguments. But it's pretty disappointing to be arguing with people who say being gay is a disorder when sexual orientation isn't a treatable condition in the first place, or the even more common tendency for people to say it is a lifestyle choice they don't have to like.
Contrast these people with the ones who say stuff like "It's 2015, who cares?" (some thinking they are giving the right response by being dismissive, others actually trying to avoid having to see gay people and coming outs acknowledged) while discussion bombs are still being tossed around. Clearly, there's reason to still care in 2015.