I haven't said anywhere that you shouldn't criticise the manager, or anything else, on here. You've taken it upon yourself to suggest that, for reasons known only to you.
What I have suggested is that when voicing those justified criticisms, it would be more enjoyable and useful to read structured criticism or debate, rather than the same old posters spewing out bile towards the manager or player in question, or even to other supporters who choose to challenge their view. Calling players "dogshit", calling Blades fans"pigs" or "Wilderettes", or posting simply for the purpose of trying to put other peoples opinions down by making a series of wrong assumptions about motive (as you have done here) is tedious, and reminiscent of junior school playgrounds.
My comments have nothing to do specifically with Wilder, or Selles, or any other manager. That is another wrong assumption on your part. Why do you suggest that to be the case? I'm talking about supporting Sheffield United.
Vocal support of football teams has never won a football match by itself. There are, however, innumerable examples of it inspiring teams to raise their standards and play better. It also tends to make the whole matchday experience more involving and enjoyable for all, which is surely the point of going to the match?
As for the 'two way thing', I'd certainly agree that good performances make it easier to raise a positive atmosphere - that's a statement of the obvious. However, this idea that the team have to give us something to get behind is just a lazy excuse to blame somebody else for our own shortcomings.