Of course MC is going to save Renge. Renge tried to kill someone based on a letter she didn't even fucking finish reading, and without even hearing him out, but she's a girl, so it's enough for our cute white knight.
Actions have consequences who woulda thought. tho in this case id put more of the blame on sorte then the girl (renge should still absolutely face consequences but i mean if you got a letter detailing from your close friend that they were enslaved and being abused youd prob rush over too, so its kinda understandable)