This is the current conundrome isn't it? And probably the reason, why so many in the debate seem to have such polarized positions. It is possible to want a players role changed (or even gone) while acknowledging how important he is to you.
I see your point and you are right, overall result will influence perception of an individual performance to a degree. But your premise in this debate is faulty to a degree because you act as if the fbref stats are a 1:1 "translation" of the game into numbers. Which it isn't necessarily. Don't get me wrong, I am not going to dismiss those numbers at all but obviously there are still things on the pitch, that aren't measured yet or ever will be. Like attempted long balls with low percentage, number of rushed decisions, perceived frustration levels and so on. Obviously - such factors are tricky to handle but they are part of the game just like the ones, that are measured right now. Which by the way is way more than what was measures 10 years ago or even 20 years ago.
If you thought, he had a good game, that is fine. Everybody deals with his own biases, what I can tell you is (and that seems to be the case with other posters), that his outing against BOU was frustrating to me because we have seen a typical "It's not going well"-Bruno performance in the last 30minutes. Hitting Hollywood passes, losing battles in midfield and so on. And it isn't just posters around here, iirc Neville was critical of him, Scholes is often critical I'd be shocked if he weren't last weekend. Same applies for McKola or UnitedPeoplesTV, at least the 2nd usually a big fan of the player from what I know. And it isn't just them, I follow a few Uniteds fan channels and most of them noted him as having a rather bad game. Not saying those people are the be all and end all, but it sets a little context.
Just saying it is overall frustration and agendas isn't going to cut it. Chelsea was disorganized, we seemed really up for it, against the Blues we pressed very differently then we did against BOU with more or less the front six playing very high most of the time. It was a very different match and while I would agree, that it is probably next to impossible to use a measure of good or bad to sum up a performance in a way that is accepted by many different people in a fan community, I think, your reasoningis not as solid as (you appear to) think.