It isn't clear from our post if when you passed these guys you were going considerably faster and they sped up to get on your wheel or if you were going barely faster and they ended up on your wheel without changing their effort.

In the first scenario, you did not invite them to be there and had no reason to expect them. So if you blew a rocket and got one of them, well, he did have the option of saying he was there when he arrived. I say no foul. HE got what he asked for. In the second, passing someone but not fast enough to get clear of them, you may be hampering the ride he wanted to do if you weren't there. You have some obligation then to be civil.

When I don't want to ride with the person I am passing, I do my best to do it decisively. When I am riding alone and someone passes me barely, then pulls in and slows, forcing me onto his wheel or to slow, I consider that rude. Yes, it does make my ride easier, but that may not be what I want.

Ben