Why do so many players start off the match being negative?

I had two ranked games today, both as Ironfist. At the start of each game, someone questioned my choice, saying things like, “I’m not sure about Ironfist,” or “Okay, worst DPS pick.” In the first game, I was ace most of the way through and had the same number of kills as the other two DPS combined early on (who were the ones complaining). The second game was just as quick and easy as a game can be.

I just reached Diamond 3 tonight, and I’m willing to switch heroes when I’m not doing well. However, before we start a game, we should always be starting on a positive note.