Thats so gay is not okay?

Why so gay?

The meaning of the word: Gay is when a man and a man or a woman or a woman love each other and are physically attracted.

FUN FACT: The term gay was originally used to refer to feelings of being "carefree", "happy", or "bright and showy".

These days’ people (mostly children or teenagers) use gay in a negative way. “Did you see Carl today? He is wearing a pink shirt” “That’s so gay”.
Actually today, I’ve heard “that so gay” more then 10 times used by teenagers.
 I’ve went up to 3 of the 10 people who said “that’s so gay” and asked them what do they mean by that’s so gay?
Answer 1: I don’t know it’s another term for stupid I guess.
Answer 2: It means …. Uhh stupid or that it’s gay… I mean … I don’t know…
Answer 3: It means it’s stupid or I didn’t like something so instead of stupid I use gay… Did I offend you or something, I don’t mean gay people are stupid its just a really bad habit.   
I’ve asked some of my “gay” friends do they get offended of that’s so gay. Most of them are used to it and some even say “that’s so gay”
What do you make of it? Should gay men or women get offended?
If you think about it there are a lot of words that are like the same but they mean differently… what do you think?