I agree. Telling people what they can’t discuss is anti-productive nearly all the time (almost put all the time, but things to do with people are rarely “always” or “never”.)
Boris Johnson is a master of dealing with stuff he wants to avoid talking about (he gets plenty of practice since he regularly cocks up).
His main 2 tactics are “throwing a dead cat on the table” (that is do something strange, bizarre, unexpected so people talk about that rather the thing he wants to avoid) and just hammering away “there are much more important things we need to talk about”. (For example, his main riposte to Partygate is just keep trying to move discussion onto Ukraine, immigration, and cost of living crisis.)