I tend to agree with Wei Dai, and it seems to me that your analogy between the way people behave on the internet and the way people behave in person is flawed.
The other difference when calling a ‘she’ a he’ in real life is:
If you can actually see her with your eyes and you call her a ‘he’ then it probably means you haven’t noticed her breasts, don’t consider her facial features to be differentiated and don’t even have a polite, respectful appreciation for her feminine form. That makes the situation extremely embarrassing for both parties.
The other difference when calling a ‘she’ a he’ in real life is: If you can actually see her with your eyes and you call her a ‘he’ then it probably means you haven’t noticed her breasts, don’t consider her facial features to be differentiated and don’t even have a polite, respectful appreciation for her feminine form. That makes the situation extremely embarrassing for both parties.