Why was being on the Glee club frowned upon?

Yeah... I know. They weren't "accepted" until they won Nationals. For a show that was very "anit bullying" it was FULL of bullying and I've never seen anything like that in High School. The show did have an off-balance "comedy" with what was made fun of and what was "not Ok" to be made fun of.

Even when the cheerios would not think they are cool, but then do "numbers" with them...

When I was in high school it was viewed as a nerd club same as chess club. I was in theater and we were higher on the social scale while glee was at the bottom. I never understood it

Because back in the 00's singing was seen as an uncool and embarrassing activity to partake in, so if you showed enthusiasm about it that suggested you had a serious character deficiency.

Wanting to sing or express yourself is embarrassing.

It is more than singing. Rock stars were worshiped, being in a band is usually equal to being popular.

Glee club is a choir and singing under the supervision of a teacher. It is an old tradition, I don't think it is something considered to be cool or anything.

Singing covers was very unpopular once upon a time, in the same way liking superheroes was unpopular. Glee actually helped change that perception along with the rise of YouTube singers, but I know even in the first season a lot of people were like "cover songs? Gross!"

I moved a lot and went to many different schools. Some schools were know for their football team, some known for basketball, some known for sciences & so on. The school in Glee is known for football. Every other group is looked down on. That’s how high school seems to work