Bikes have equal rights to lanes as cars. Learn the law.

He could be riding an elephant and it wouldn't matter. The bare legal minimum is not the standard for what constitutes good behavior He'd being dis-courteous to other road users. He shouldn't complain when some of them let him know.

Regardless of his mode of transit if he's going below the prevailing speed and avoiding taking opportunities to let others pass he deserves to hear about it in a not nice way.

Not that it's applicable here but it's doubly true so if he could simply go faster and conform to traffic norms but chooses not to (this is why a speed limit following Prius catches more shit than a laden truck that can only go that fast).

Blocking the lane by going a few miles an hour above the speed limit?

how are they blocking when they are going 28 in a 25. Speed limits exist for a reason.

It’s the same old “rules for thee but not for me” thinking that’s pervasive in some circles.

Why does "blocking the lane with a bike" matter in the slightest? Maybe some people see that as a personal affront because they think the road belongs to cars?

It's only "blocking" because the drivers think the bike is too slow. Which is because they want to break the law themselves and speed dangerously. It's pretty bogus.