The question is can I go back to Slog? And is Deacon against me now? Or should I just go back to a previous save and leave the deathclaw alone this time.
go back and see if they forgive you. if you are on PC there is a command to use I believe.
if not, then reload a save.
good thing you stopped any forward progress to correct it! better than finding out later!
Yea fights with NPC's around can get real frustrating. In the U.S.S Constitution quest I had a heck of a time finishing it without accidentally shooting one of the robots who would rush in front of me as I fired then of course they all went hostile. I had to reload that one several times.
I tried giving a Brotherhood solider who was on low health a stimpak by pick pocketing him. I just wanted to see if he would use it. However my pick pocket failed, he caught me trying to help him & the whole brotherhood turned against me. The moral of this story is... when something like that happens I find it best to reload.
Same thing kept happening to me. Over and over and over.
Generally, it takes 3 in-game days for the settlers to calm down, so they'll be red in the meantime. You can always try this:
Find a named settler and draw your weapon. Be sure you're in their line of sight. As they approach, lower your weapon. Sometimes this resets them, though it's not guaranteed. You can try several attempts to see if you can succeed. If not, just leave the area for a bit.
My guess is you probably inadvertently hit a settler going after the Deathclaw. Something as stupidly incidental of flying debris caused by your shot can trigger them against you, so it's always best to take the fight to the enemy, not allow the enemy to come to you (or the NPCs).