Mike and Stef’s fight just shows how none of the adults believe Callie loved Brandon.
No one has any problem believing that Brandon is genuinely in love with Callie, it’s completely plausible to them that he was hurt. Stef even said that she knows Brandon’s heart was broken, and Mike thinks that it hurts him seeing Callie hook up with AJ.
But nobody legitimises Callie’s feelings for Brandon.
Instead she’s either cast as the ’victim’ by Stef, or she’s practically being slut shamed by Mike, who thinks she led Brandon on and “toyed” with him.
This is just another example of how Callie’s feelings and wants are ignored, and how assumptions are made about her without anyone actually giving a shit about how she’s feeling.