Everyone has their own risk tolerance, but regarding jumping to conclusions, I wouldn't make any assumptions at all. I wouldn't assume that he's smart. I wouldn't assume that he's stupid. I wouldn't assume that he has me in sight instead of some other aircraft. I wouldn't assume that he doesn't. I wouldn't assume that my brakes will fail. I wouldn't assume that they won't. I wouldn't assume that an unexpected tailwind might come up. I wouldn't assume that it won't. The only action that takes into account all those possibilities is a go around.
Hmmmm, not sure if you ever studied either stats, or logic in school.
Your commentary seems to indicate that by making an 'assumption' in both directions that the probabilities are some kind of equality. I'm now going to give a SWAG that the probabilities of a complete brake failure in a GA plane are < 0.000001 (~1 in 100,000) applications, I am going to 'assume' that my brakes will work.
Next, if your tautology is to be expanded to the logical conclusion, you've decided to power up and go around. Might as well use the same logic on the assumption that power will be avail, flaps will retract right, you won't stall it, etc. There are risks with each decision, and they are quantifiable. The question I have is which is safer?
Since the OP stated the plane made a call that they would 'line up and wait', that tells me they know there is traffic coming, otherwise they would just announce taking off. Again, I'm going to assume that the guy who said he would wait - will actually wait. My assumption is based on his statement over the radio. So, I'm in the final throws of landing, I'm going to land, and take the energy out of the equation. Worst case, I'd rather hit somone at 20-30MPH on the ground, than risk hitting them at 60MPH in the air.
So, I would say your go around theory being safer has some holes in it.