Funny enough, the most rotten attitude I've dealt with recently was another tank when I was tanking an 8-man. Absolutely toxic player. We almost halted T4 so we could kick him for harassment. (Not naming names, but he's on Exodus. He was so bad I looked him up to see if I needed to blacklist him on my server.)

If you go into content with a cheerful and positive attitude yourself, most people make an attempt to reciprocate.