You could probably make an argument to not thaw people who are still considered bad by the people doing the thawing.
There are two ways such an argument could go. One is that not-thawing is punishment. He was a bad guy and wasn't punished enough during his lifetime, so now we will punish him more by not thawing him. That argument, as you imagine, has some problems.
The other way is to say that this guy is a danger (or, more generally, a net negative) to the current society. But there are problems here, too. Let's take everyone's favourite -- Hitler. Is he really a danger to the society, say, a couple hundred years from now? Or maybe, given the lack of very unhappy Germany, he'll settle down in some pastoral village, make speeches to the walls of his cottage and work on improving his art?
The question isn't as easy as it looks.
There are two ways such an argument could go. One is that not-thawing is punishment. He was a bad guy and wasn't punished enough during his lifetime, so now we will punish him more by not thawing him. That argument, as you imagine, has some problems.
I can think of two situations where you might want to do this:
This month's media thread includes a short article on some people's idea to have Ayn Rand frozen, which ultimately didn't happen. My first reaction was a shudder. I thought, I definitely wouldn't want Ayn Rand preserved forever. My second thought was, What right do I have to say who can and who can't get frozen?
Whatever your thoughts on Ayn Rand, I think this can spark an interesting conversation: What, if anything, should humankind do about people who are widely seen as harmful for the whole? For example, if the Castro dynasty in Cuba or the Kim dynasty in North Korea decide to freeze themselves to ensure they will continue oppressing their countries forever, should that be prevented? (And yes, my opinion of Ayn Rand is such that these examples came to mind.)