However your caution is warranted. Even if the person saying “that’s dumb” is a nice person the listener might not know that, or might have been conditioned by someone like what you describe.
Years ago I was on a panel: there was an organizer (who chose the participants) and me. The first words I spoke were, “I think [organizer] is completely wrong and in fact has things utterly backwards.” We spoke for a while and as we walked off stage, Organizer said with a smile “That was great. I think it went very well”.
As we parted an audience member came up and said they were shocked at how hostile I had been to Organizer.
I happened to know both people and they had attended MIT as well.
Moral: jargon is contextual jargon, even if it consists of ordinary words. Think of your audience.