I don’t really understand this thread.
As some mentioned it obviously depends on why Reuvein avoids cs.
If he considers it assur then obviously Shimon shouldn’t serve him issur (and of course keilim are a problem)
If he views it as an easy way to show how frum he is. This is the best opportunity to show off! Of course he should insist Shimon spend extra to accommodate him.
If he views it as muttar but only beshas hadchak or as a way to be closer to the Ribono shel oilam he is machmir. Why would he impose this on someone else? And at the Same time why wouldn’t Shimon make an extra effort to accommodate his friends genuinely held chumra. They should be fighting with Shimon insisting on only serving cy and Reuvein insisting it isn’t necessary.
Maybe that is what the op meant