What similar trash could they have talked to saying they wanted to hear if she screamed like a man or not? Is it possible transphobia is one of multiple motives for their murders? Because the transphobia is certainly there, and that's an explicit statement by one of the killers of their motives. Are we just ignoring that or explaining it away that they said it because it's talking trash? If that's the case why should we believe they just wanted to experience killing somebody? That's based on what they said too. Why believe one and not the other? Why is it so hard to believe they're transphobes, but not that they're murderers?
They may have multiple targets planned, but they only murdered one person. That person was trans, and the fact that they went so far as to call her "it" and expressed wanting to see if she screamed like a man suggests that was not a non-factor in their decision making. Anti-trans sentiment would be better combatted by drawing attention to it and calling it out when it happens. Not denying that it exists or that it is significant. Obviously their desire to kill someone may be a primary motivation. But transphobia was absolutely a secondary motivation, and it does a disservice to Brianna to deny that.