Why are people so miserable in QP?

I only play qp, I like Overwatch to just have fun and let off steam, but this is the first time I tried to learn DPS, and match after match is people who just are so toxic. Why is this? When I'm playing tank or support, they are usually friendly. But when I played DPS yesterday, they constantly are just rude man. Whats up with that?

https://preview.redd.it/5687h6l5hegc1.png?width=476&format=png&auto=webp&s=db1dc19277c11a0ca9d8be21de0a57e04e91c30e

https://preview.redd.it/21p6g116hegc1.png?width=471&format=png&auto=webp&s=b75be1c39d00fddb85dfc160696819d7a49707f6

https://preview.redd.it/90mgjmp6hegc1.png?width=500&format=png&auto=webp&s=467fa34df7959cc267ed31e995ee9a8f10c05b3b

Edit: Thanks for the replies, I was not aware of the mute of chat option, I will do that in the future when trying out dps, thank you!