Responding to low-key insult from lecturer
Sincerely? Let it go. The tone is also not "low-key insulting" (that means a personal disparaging attack on you), it is dismissive/snotty/irritated (do not bother me with this stuff).

The thing is that you are reading a lot (IMHO too much) into this. I'm not saying that you are wrong, but it sounds that you are in danger of spending precious lifetime for collecting perceived slights. You have already used approx. 1 hour of your lifetime to ask this question, and probably several hours of suppressed anger pondering his answer.

Really, the easiest way is to think "Perhaps he has eaten something bad today/has relationship problems", or whatever. Remember: once is chance, twice is coincidence, thrice is a pattern. If it happens three times, then it is time to act.