”I was only a monster when I had to be” - why is Negan so unrepentant and still defending his actions in DC?

Dead City 1x02 makes it seem that Negan murdering Abraham, and especially Glenn, was somehow necessary. And it seems quite insulting to say that to Glenn’s traumatized widow as well as his legacy and memory.

If Negan were to be reformed, he should be in lifelong guilt and shame over what he did, not even being able to look at any of the people he hurt, instead of bouncing around and being his old self again.

What do you think?