I think that the written word is often open to wider interpretation than the spoken word. The tone of voice, a remark with a smile could mean a comment be taken in a totally different way when written. This would obviously not apply to downright rudeness, but could be the reason that some read a remark as offensive. Similarly two people could have a totally different reaction to a comment that they read, but if the comment was spoken they might well have the same reaction.
I have received a couple of unpleasant remarks in the past, but have chosen not to get into an argument, not because I avoid confrontation, but because a) everyone is entitled to their opinion but mainly b) I can’t be bothered.