Maybe it's just that our definitions don't match. When I think of "invalidating" someone's feelings, I think of downplaying them, refusing to acknowledge them, or even denying someone's right to have that feeling. Think of comments like "oh, you're just PMS'ing", "don't fuss, how can you make this into such a big deal?" or "you're white/black/male, so you're not allowed to feel insulted about this".

No, what I mean is not closer to "your feelings are dumb" either. Telling someone to fuck off is communicating that their /presence/, or their /attitude/ is unwanted. It doesn't directly attack their feelings at all. It may be uncaring, and the recipient may still be hurt by it, but it's a far cry from denying people their right to feel.