First off, the two or three people "in your way" were only looking to get a quick photo of the parade so they can look back fondly on the day. It's not like they were trying to stand around and block your view. Even when these people came into your precious space for a few seconds, they were clearly making their best effort to crouch and not to block your view.
Secondly, if your going to be so protective of the view, could you try and be a little more FUCKING polite (irony, i know). Instead of immediately flipping out, try asking people a little nicer. The parade moved at a pretty slow pace, so it was very hard to miss anything that was going by. You didn't hear people around you who were short or with kids screeching at people to move.
This seems kind of insensitive, but if anyone was in that area, you would know what I'm talkin' about.
---Don't rain on my parade