Wolf,
A pilot's reaction to a hazardous situation depends almost entirely on their training and experience. If you look at the actions of the tow plane and the response of the guy with the vid camera, you see two completely different reactions, but neither is entirely correct.
The tow plane pilot saw the impending collision and made a very aggressive climbing maneuver. This would be fine, except that he's towing a banner that hangs up to around 100 ft below his plane so he not only has to maneuver his own plane around a collision, he also needs to consider where he's maneuvering the banner. A more appropriate maneuver may have been to push over and dive.
The other pilot saw the near miss, and immediately began what you might call a "wtf?" gentle climb. This is very nearly instinctive and is what you would expect from an inexperienced or untrained pilot. There isn't much that would have been more appropriate except for a better visual lookout and a deliberate maneuver (or non-maneuver) instead of the sort of wimpy gradual climb that like I said, is what you'd expect someone who has no plan or idea what's going on would do.
Most pilots I've flown with, including many many students and even myself when a new pilot, will begin a gradual climb when unsure of what's going on and when reacting to an unexpected situation. Even if this is a totally inappropriate response, this is still the natural tendency. For example, pilots faced with a reducing ceiling of clouds will often pull up into the clouds instead of simply turning around and remaining VFR, and pilots who have an emergency situation when flying below a cloud deck will also often climb into the cloud instead of troubleshooting VFR. Negative G's are very uncomfortable, emergency maneuvering, and unusual attitudes are not generally taught to private pilots to a level that really give them full mastery of their aircraft. As evidenced by the results of the airbus incident where pilot actions and screwed up rudder deflection gains in the flight control software resulted in the pilots ripping off the tail, even professional commercial pilots sometimes do not receive sufficient training in how to aggressively maneuver their aircraft WHEN NECESSARY. That training not only teaches them how aggressively fly their plane but it also teaches them how to identify a situation where aggressive maneuvering is required and how to select and immediately implement the appropriate maneuver.
When I'm flying and I see an impending collision, because of my training I am just as likely to push over to avoid the collision as I am to pull, because I've been deliberately taught to pick the appropriate maneuver instead of just blindly pulling on the controls when things start to go bad.
In that video, IMHO the tow pilot should have pushed over and the other dude should have either continued to fly straight or made some sort of immediate aggressive maneuver. The middle ground, wimpy "uhhh I"m scared so I'll just sorta climb a bit" response is rarely helpful.
That said, there is no substitute for a good visual lookout. I don't really think poorly of the pilots for not seeing the other plane because I've been there and just about run into a few other aircraft in my 18ish years of flying, but they almost died because they prioritized something above their visual lookout and it bit them hard.
