I'm pretty sure he wasn't saying to leave them unlocked indefinitely. Some companies lock accounts as soon as they lay people off (or even before), because they're paranoid that someone will grab trade secrets or sabotage something. Treating people this was is really insulting. It's generally reasonable to let people retain access for a short period of time (i.e. the rest of the day) so they can do things like send goodbye emails to the team, grab the e-tickets (or whatever) that they had sent to their work address instead of their personal address. No one should expect their accounts to remain unlocked for long, but long enough to close out any open threads and say goodbye is just being respectful.
Ever been in a roomful of people waiting for a suddenly-called all hands meeting, and seeing a whole bunch of people with their phones out wondering why their email isn't checking, then seeing their wifi credentials stop working, then the lightbulb going off in their heads?
