"Any [person] who [disagrees with me] is [committing an error]" is a thought-terminating statement. Best to avoid using that kind of language -- it doesn't particularly hurt anyone else, but it will hurt the growth of one's own understanding.
On the other hand, sometimes people are just not correct, due to motivated reasoning, and keep asking the same question ("Is this an illegal security?" "Yes") over and over again hoping to get a different answer. Ultimately you have to terminate thought somewhere or you get bogged down in trivialities by people who are trying to exhaust you.
