Hmmm, so lets all stand around and high five each other 'cause our friends just got laid off and we didn't. Hey, they took one for the team right? Tell their spouses and children that.
Just so you know, you're right. I know ABSOLUTELY NOTHING about congratulating someone for laying someone off because it's not something a reasonable, or caring person would do.
Go ahead and email your congratulatory email to your boss Pooj. When your times up (which I hope it never is) then feel free to email him again and congratulate him on doing what was "necessary".
Best advice, like CBF said in a prior post, "let your work do the talking".