Being unable to engage with certain viewpoints to the point of bringing up foreign infiltrators every time you see it is a sign of brainwashing. I stated that as calmly as possible. I have received far worse replies on this forum.
What really derails the conversation is needlessly tone-policing people. People have a tendency of only doing that to opinions they disagree with; so in practice it's just another way to start a flamewar.
I commented on your tone exactly because I frequently find myself agreeing with you when other people don't. If I disagree with someone in both content and tone, I won't bother engaging, I'll just downvote, flag and move on.
What really derails the conversation is needlessly tone-policing people. People have a tendency of only doing that to opinions they disagree with; so in practice it's just another way to start a flamewar.