I don't like it, but if he dropped the dime on his boss (which may be a foreign government), then he's going to get off lightly. Likewise, if we are running a counter-intel operation, then we'd make sure that he'd get a light sentence (the harsher the punishment, the more you signal that Berger got something important).
Why should he be considered for a security clearance again? Because if he doesn't have said clearance, then he is technically barred from revealing certain things that he knows as our former National Security Advisor...say, at a trial or to our intel agents.
There is also the strong possibility that Berger is a double agent. In which case, he'll be used to send false intel to a foreign client.
Spookville is a different sort of city than any other town. The roads and rails run backwards there, and all is not as it seems.
This is a situation where we can't really have an informed opinion.
I'm not sure I follow your logic here. How can Sandy Burglar be "technically barred from revealing certain things that he knows as our former National Security Advisor...say, at a trial or to our intel agents" if he doesn't have clearance? People withOUT clearance are required to reveal information to people with clearance all the time. He can hardly claim that if he has the clearance, he'll remember things, but if he doesn't have the clearance, he won't be able to remember.
He was, in my opinion, a low-hanging fruit, and there is more to come, in the court of public opinion or in the court system, for his prior boss(es).