Definitely agree. It's difficult to convey that level of charm / diplomacy via text, for me at least. Body language and other props being available also play a big role in making someone switch focus, and at least feel positively about the overall interaction, even if I ultimately agree to disagree (and state that, or not).

If I feel as though the online recipient of my messaging isn't receptive, there's really no need to contend in the first place. I don't have to change everyone's mind, nor is it really my place to do so ...