I’ll ignore the obvious boilerplate (first paragraph). TL;DR: Yes, I’d suggest removing the use of in-/humane completely (same for the German counterpart un-/menschlich). But not because I think the definition is bad. That argument could also be made: It really is an empty word that people attach any meaning to that fits their current purpose. But that’s really not my argument. It seems you’re familiar with syntax vs semantics, so I’ll omit that wall of text. But, one example:

The elephant eats the peanut.

The peanut eats the elephant.

Both phrases are syntactically correct but the second is semantically incorrect. A peanut cannot eat an elephant. It’s the same with at least both words, humane and inhumane, in tandem. They are semantically incorrect. Humane denotes a set of human characteristics (yet, it is a real subset). The in in inhumane implies there is no intersection with the set of human characteristics. Yet, everything labeled as inhumane is part of the set of human chracteristics. The in in inhumane also implies it is the opposite of humane, which makes no sense if they are both subsets of the same set. No matter how you turn it, both terms are logical contradictions. And that’s also why (imho), whenever they are used (at least most of the time), the statements containing them are nonsense.