They're invested in PC gaming as social capital where the performance of your rig contributes to your social value. They're mad because you're not invested in the same way. People often get defensive when others don't care about the hobbies they care about because there's a false perception that the not caring implies what they care about is somehow less than, which feels insulting.
Don't yuck others' yum, but also don't expect everyone to yum the same thing.
Very well put! I'd also add that most people aren't even really conscious that that's the reason that they're mad. There's ways to express your negative opinion without stating it as a fact or downplaying the other person's taste.