Overwatch has had a toxicity problem since day one. I suppose that is nothing surprising for an online game, but it has been around for long enough now that everyone thinks they're an expert with a deep understanding of the meta. It can get heated when a discussion (flaming) happens around suggesting (demanding) players switch heroes.
Thankfully, the game is taking a big step next week to fight the toxicity. In a talk with PCGamesN, director Jeff Kaplan announced starting this week, if you report a player, you will get a notification in game if action is taken because of it. He explains:
If you've reported somebody and they've gotten actioned you'll be notified in-game. We've done a pilot program where we were experimenting sending emails to people. As of that Winter Wonderland patch we'll have the technology to do it directly in the game. Hopefully that restores some of people's faith in the system and then they use it more.
On top of this, players who are close to some kind of punitive action will get a warning encouraging them to just be cool for like a second.
While this is hardly going to stop toxicity all together, it will likely encourage players to use the report feature more often as there will actually be a back and forth dialogue instead of it feeling like throwing a bottle into the sea. Here's hoping it helps.