I tend to become toxic myself when I encounter incompetent players in max-level content or players who insist on teaching new players completely wrong things. It does indeed matter, if you are a non-tank, not to stand in front of the freaking boss in old content, whether it's the Crystal Tower raids or not.

When you get constantly cleaved from the boss and end up dead in the dirt, you're not being helpful to anyone and simply becoming a burden, especially for the healers who have to keep resurrecting you.

Or when players intentionally misuse boss mechanics or use their own abilities to intentionally kill their teammates.