In "Masquerade", Matt is clearly very pained as their murder suspect recounts having been raped by the victim and then stabbing him in self-defense. Then when talking with Natalie and Ronnie, he cheers her on—"Good for her for fighting back". It seems as though he's simply been given Curtis' lines from the original episode, until you recall that the girl's story is very similar to Alesha's and he's actually expressing his lingering anger over her ordeal.
Matt flipping out everytime Ronnie's in danger can seem excessive. But not when you remember that his father/stepfather was absent and/or abusive. Of course he's going to flip out. Ronnie's the closest thing he's had to a father and he's terrified of losing him again.
The episode "Deal" ends with Ronnie frantically trying to tend the injured Matt. "Survivor's Guilt" begins with the now stunned Ronnie still at the crime scene, watching the technicians at work. The horror is in realizing that Matt probably never made it to the hospital, otherwise the episode would have opened there. Which means realizing that he must have died at the scene. Which means realizing that poor Ronnie probably had to endure watching his partner/friend/surrogate son die right in front of him, completely powerless to help—and he's already lost a partner to violence. Plus the fact that only minutes before Matt was shot, Ronnie was gushing to him about the birth of his grandson, which means that one of the happiest moments of his life will forever be associated with one of the worst
There's also the matter of the wife and son of Matt's friend, left widowed and fatherless, respectively, when his friend killed himself, who now have to contend with another devastating loss, probably coming just as they were beginning to recover from the first one. It's especially bad for the boy, who clearly viewed Matt as a big brother/uncle type and whose relationship with Matt would no doubt have eased the pain of losing his father—only to lose him too.
"Hard Stop": Wes is killed and although no one on-screen mentions it, longtime viewers know that this is now the THIRD time Ronnie has gone through this