Merely attempting to enforce a copyright that you legitimately hold against one instance that might be fair use, and then having a court find in a real case that it was fair use, would be enough to lose copyright of the work entirely in your view?

That's so disproportionate that you might as well just abolish copyright.

Also, most of the world doesn't have fair use like the US does, though many places have similar but weaker provisions in some respects. US fair use law is somewhat controversial, because it arguably doesn't comply with international obligations.