Batman seemed to have no qualms about killing humans, so I don't see why Superman having a mom would matter all that much.
Even if we assume that's right and it had nothing to do with them both being named Martha, it's still stupid as shit. It makes Batman look like a crazy fuck who didn't put the least bit of thought into this before deciding that he had to murder Superman. Considering how determined he was, there is no way his mind should have been able to change that quickly.
And, if Martha's name wasn't important, they could have just had him say something like "my mom" or "Lex has my mom" like a normal person would have. Considering how they went out of their way to make him say his mom's first name, obviously they thought it was pretty important.







