Earlier quoted context omitted.
I also don't know what I'm talking about, but I think one of the core responsibilities of a trademark owner is that you establish a history of defending it. I heard once that if you don't do that you risk losing control of your rights to that property. Any smarty pants on here able to confirm/set me straight?
If not making a fool of themselves in the process, yes. Common sense is much needed in such situations, I would say.
I'd guess that the cost of making a fool of one's self for trademark enforcement is usually pretty low... especially if your target customer doesn't make purchasing decisions based on it.