The only problem there is that Carter Page has effectively been “outed” already anyway — just based on everything that is publicly known about the guy. He’s so fully exposed that the DOJ didn’t even redact his name from the documents linked in the article.
Hard to see how revealing this source, if it IS Halper, would affect national security in any meaningful way. He is 73 and probably at the end of a career as a spy.
As a professor Halper was probably an associate of Christopher Steele from MI6 days who could act as a cutout with plausible academic credentials -—and provided with some DNC/Hillary cash to spend on trying to entrap the two Trump academics. Fringe academics like Pappadoupoulos and Carter Page are always short financially and willing to ‘consult’ on anything that will bring in some money.
All the small group in the cabal against Trump needed was a wrong answer to a leading question to be able to open an investigation that was probably phony from the beginning, instigated by the desire to spy on the Trump campaign.
It appears they were lambs led to slaughter. Seems rather cruel to use them like this, especially considering the outcome of the brief and their minimal contacts. They get “outed” but the entrappers are shielded??