Using the word 'gay' to describe somebody who is homosexual isn't an insult, and is actually a word used to describe a persons sexual orientation, as used by networks and communities to describe people who are not heterosexual, i.e. LGBT (Lesbian, Gay, Bisexual and Transgender).
Using the word 'straight' to describe somebody who is heterosexual shouldn't be taken as an insult either...
Using either expression shouldn't be considered hate speech either.
I will add this regarding the usage of the word 'gay' - as pointed out, gay referred to somebody who was carefree, happy, or 'showy', as in 'what a gay day' meaning 'what a happy day', (a phrase which became a catchphrase of the entertainer Larry Grayson). The word was later used to describe a homosexual person, quietly replacing the original usage in modern language.
'Gay' is also now being used to describe something rubbish or stupid, especially among younger people, which obviously causes some issues as some observers draw a connect between the current 'accepted' use of the word. Often, to avoid word filters or accusations of homophobia, the word is written as 'ghey' especially online, and has come to be accepted as referring to something that is 'lame'
