But we all already know that many do not approve of Bush, do we not? So where's the good in that? What's the new information we're supposed to gain from these protestors? They're telling us something that's common sense, something we already know... in every election, there will be tons of people against the sitting president and wanting him ousted. That's a given.
I think that regardless of your view of the Republican party (or the Democratic party, for that matter), anything that would draw attention to either the Democratic platform or Republican platform (in the interest of having informed voters) is good. So I'd have to disagree that focusing attention on the RNC is a bad thing. Informed voters (and ideally, this would be every voter) should watch both conventions, as well as any debates, and vote according to principles and conscience.
As for your other two points, I agree.
I have mixed feelings...
Gives attention to the RNC: Bad
Shows that MANY do not approve of Bush: Good
Clogs up city streets: Bad
Net loss for the city: Bad