Good points, zyxwv 
One thing to add. Like you, I am usually silent when non-tippers keep asking the performer to do things and keep asking everyone else to tip.
However, I do sometimes say: "I will tip again when you tip, xxxxxx".
It usually works. Sometimes member xxxxxx stops his incessant posts. Sometimes we get an apology or explanation of why xxxxxx doesn't have any credits. And sometimes member xxxxxx tips, and I then tip again. That is the best result 
That seems like a good idea, ronnie-uk. Sadly, I cannot tip very often, being on a tight budget--the models I visit know this and are apparently okay with it because I do not make requests, and because I do tip or go into private when able.
With regards to the situation you describe, though, whether I have credits or not, I sometimes say to member xxxxx after they use that obnoxious "Let's Tip" emoticon (without tipping at all themselves), "start us off, xxxxx". That also tends to either shut them up or get an explanation...or an excuse.
One thing I really dislike, and which I've told off other members (probably basic members) for, is when I tip "just because" and someone else tries to use my tip to get a model to do something. I'll tell those other members to send their own tips (though perhaps not in such polite language). The tips I give are between me and the model, and if I don't ask for anything at all (or at most a smile), that's my business, and no one else should expect to take advantage of my gift to the model to satisfy their own desires and whims.
Quote