This is ascribing motive, the post 405 says “your overriding tendency is to treat them as monolithic” —> and besides attempting to ascribe motive, it is being personal. Instead of focussing on the issue, the post is ascribing motive
For instance, if I said "that's a strawman argument" or "you're arguing against something that doesn't exist" or "you're treating my denomination as if it were a cult" - none would be attributing motive or mind reading. They would be expressing my own mind, judging your posts not you.
But if I said "you are just saying that to make me mad" or "you're making a strawman argument to change the subject because you have no real defense for that" or "you believe my denomination is a cult" - any would be attributing motive and/or mind reading.