You can derail any discussion by asking for definitions. Human languages is magical in the sense that we can't rigorously define anything (try "Love", "Excitement", "Emancipation" or anything else, really) yet we still seem to be able to have meaningful discussions.
So just because we can't define it, doesn't mean it doesn't exist.
It's not a derail, it's an attempt to understand the other person. If I say Thing is bad and you say Thing is good but we haven't actually defined Thing, then we could be talking past each other and not actually be in disagreement. Text over the Internet is such a limited medium.
So just because we can't define it, doesn't mean it doesn't exist.