"How is that so different than what Betty did, or what the millions of other women who continue to take their husbands’ names do? One could argue that what most married women do is more problematic because, unlike Don, most of them don’t claim a horrific past from which they legitimately want to escape, they just want to be identified as something else."

One could argue that, but not effectively.

Don says "lots of people change their names...You did" Betty says "I took yours"

There's a difference. Don stole a dead man's identity. The real Don Draper didn't have a say in the matter. A husband willingly gives his wife his last name. The wife's past is immaterial.

I just don't see how a convention of marriage is the same thing as assuming a stolen identity. Don is perpetrating a fraud. As Betty says, "You've lied to me every.single.day". Are the women that take their husbands' names lieing every day? No, they've just changed their names.

That's the point. Don didn't 'just change his name'. He assumed something that belonged to another man. At the very least it's disrespecting the dead, at most fraud and theft, and desertion. He could have just as easily deserted and really just made up a new name and started over. That's not what he did, though. And Don knows there is a difference and he was just rationalizing it with his specious argument to Betty about women changing their names.