It's usually not a good idea to conflate whataboutism with pointing out parallels from a different perspective
I don't know if I'd call them relevent parallels if what they're describing isn't really comparable beyond a superficial level. Saying "war was also morally questionable in Vietnam" in response to someone saying "drone strikes in populated areas seem morally questionable" isn't really a very meaningful response to the latter. Perhaps whataboutism isn't the correct term, but it sure sounded like whataboutism to me.
Anything can be compared. Anything. Now you're conflating something being comparable to something being equal to, and that wasn't even his point. Please don't distort the message. It was very clear, and pointing out that something has been around for a long time is not a whataboutism. These terms keep getting thrown around way too loosely, and it's irresponsible.
I'll accept if you don't like the use of that term, but I stand by his core argument being flawed:
Any sober assessment of this history must conclude that the present objections to cancel culture are not so much concerned with the weapon, as the kind of people who now seek to wield it.
This assertion completely ignores the possibility that the weapon itself changed, and that those changes have contributed to the problems with cancel culture that are unique to it. ---