When you let someone go, you should always make sure it's not totally clear behind you (and that the vehicles behind you are at a decent distance).

The other guy is right but was being cranky about you doing something a bit silly.

Stopping to let people go is advanced level driving. If you do it wrong you are fucking stuff up more than if you just did nothing.

When you get trained by a company (like Fed Ex, Verizon, etc) you are advised to NOT stop for people as it causes more accidents than not.