It is good to pre-think different situations and have some go to reactions to resort to.
I don’t think there is anything wrong with a catch-all reply like “No thanks”. It’s not rude. The sentence itself is polite. How many situations do you honestly need to prepare for?
In reality, I reject so rarely that these answers won’t make a shred of difference either way.
So if the question is ‘what would happen if a man rejects a woman without an explanation?’, my answer would be “close to nothing”.
There is a local guy who is a known celebrity at festivals who has rejected at least 2 of my friends extremely rudely with the same response. As in, this was the conversation:
My female friend: ”Can I ask you for a dance?”
The guy in question (and I quote): ”No, you may not”.
Yet I’ve also heard many other people talk glowingly about the same guy in other circles.
We can debate whether this kind of response is damaging for the scene. But if we are talking about whether these types of guys get any blowback for acting this way towards certain people, then the answer is no.
As for there being an even playing field or not, I would still say no because every scene is different. I don’t have to worry about pre-prepared answers or giving long-winded explanations if I don’t want to. But I can‘t say that I’ve never offended anyone before for giving seemingly innocuous answers, because I am 100% sure I have.
But my advice would be not to worry about that sort of thing if you’re thinking about rejecting someone. At some point, you’ll offend someone anyway either knowingly or unknowingly.