I think most people would agree that Scenario B is ideal. Unfortunately, many modern conversations about social justice look more like Scenario A. It's common, for instance, for members of different groups to argue about who has it worse.

This failure mode is often deliberately induced, as part of a larger process called derailing. For example:

A: "I feel, as someone with a mental disability, that it is often difficult for me to have my desires and feelings respected by others."

B: "LOL first world problems. Look at children in Africa and then tell me how bad you have it."

C: "Brother, us C-types have had it far worse than you A-types for far longer. Wait your damn turn."

D: "I think that your A-typeness gives you too much privilege to be complaining about people disrespecting your desires and feelings, and us D-types experience exactly the same rejection of our perspectives far more acutely than you ever will."

At which point, A can try to show how their complaints are valid in comparison (which immediately buys into the "who has it worse" misery poker), or A can simply restate "nevertheless, I feel that my desires and feelings aren't respected" - in which case, A themselves is accused of derailing, by drawing attention to their issues instead of falling into C or D's coalition, or agreeing to participate in guilt for the plight of the people that B mentioned.

On top of that, you have an actual strategic game of 'misery poker' being played, where plenty of people DO pretend to have grievances just to shut up other people's grievances, which corrupts the whole signaling playing field - since now everyone's legitimacy is suspect. Once that happens, you enter a signaling arms race, and being a good signaller becomes far more important than actually having something valid to signal.