My reaction when I first saw this was the same as most here: Ban Bos. However, after hearing his side of what happened and looking at the video many times in slow motion, I don't think he was intentionally trying to take Impey out. Watch this from about the 26 second point:
http://www.youtube.com/watch?v=tf-TuKGyDwI&NR=1
-You can see that Bos is boxed in and the barriers are not straight, they are closing off his line from the left.
-He puts his hand on Impey's side with his arm straight out, apparently to keep Impey from moving left. It doesn't look like he actually pushes him.
-Through all of this, Impey holds his line perfectly, there is no indication that he is chopping Bos at all, but Bos puts his hand on him to make sure he doesn't move left. (This is fairly common in track sprinting, where there are no barriers and no other riders to be affected. Hell, I've head-butted guys to get them to move over, this is pretty mild by comparison. Bos just needs to break his track habits if he's going to sprint on the road.)
-Almost immediately after he gets his hand on Impey, Bos appears to hit the foot of one of the barriers and loses control.
-In the split-second before he goes down, his instinctive reaction is to grab something to hold himself up, in this case Impey.
-The rest is more obvious: Bos goes down and takes Impey with him, although I really don't think it was premeditated, it was just a knee-jerk reaction to hold himself up that caused Bos to pull Impey down.
-All of the above happens in about 3 seconds, so there isn't time to think, it's all "brain stem" reaction stuff.
So I've changed my mind a bit, I don't think Bos was intentionally trying to take Impey out. Still, it was a poor decision to put his hand out in the first place, and I think a 1 month time-out is a fair reprimand that will hopefully see Bos start thinking like a roadie and get over his old track ways.