Different cultures are different, but this is the standard drill repeated from elementary school onward through workplace policies in my part of the US. People routinely ignore it without punishment, but it's there hanging over the head of everyone.
That's just not true. A hug could be sexual harassment, but so could a really dirty handshake. Let's not live in a world where we're scared of normal interaction.
Sorry. You just made me laugh out loud.
If someone asks for a hug and you don't want it, you can offer the handshake and just wait. The next time around, they probably won't offer the hug, but if they do you can do the same thing over. Nobody will seriously judge you for being a "handshaker and not a hugger".
As for doing some kind of predatory hugging, then yeah, it's obviously not cool, but I don't think any male could pull it off on a female without paying the social price.