Why is 'gay' used as an insult?

It's sad when people start losing a rational argument and then start falling into ad-hominem arguments instead (i.e. personal attacks and insults instead of logic and rational discussion).

It's even sadder that many people feel that homosexuality is the ultimate insult. Perhaps it's true that those kinds of people are worried about their own masculinity.

P.S. - It's also somewhat ironic that the word 'gay' originally just meant 'happy' or 'jolly'.

I think when they use words such as 'fag' or 'gay' then don't actually think of the meaning to the word, It seems a lot of people use this word by ending an arguement when they do not no what to say.

Its like when someone is in your class, and they find the work difficult they'll say something like "This is gay."

Obviously he doesn't actually mean the sexuality of the work, but he replaces the word hard with gay, to perhaps seem more masculine.