Some cyclists don't use common sense in traffic.
They try to squeeze through traffic and get themselves in trouble....plus this particular buffoon feels he should use his U-lock a little too hastily. U-lock swinging is for dealing with hostiles...not venting anger. Voices can be raised enough to get the point across (hey!!! watch it buddy!!!).
Pretty much the cyclist needs to realize that sometimes, brakes are a good thing. In heavily congested traffic, it's always best to err on caution, and if you do get risky, and something stupid nearly happens, to jsut accept it, since the risk was accepted by the rider whe attempting to navigate in tight spaces.
In slow speed congested traffic, I DO take the lane...anyone who has a problem with it bite me, since I'm not slowing things down much if at all....in most congestion situations, I'm actually just as fast as traffic...so why not take the lane?
On your side, from what you are saying,you were merely doing what you should in traffic. There's no rule saying you can't let somebody into the lane...actually I find that rather polite, as I know how bad it sucks trying to merge into a lane to make that turn.