That makes no sense. His peacenik and revolutionary days, which are greatly exaggerated anyway, were long over. None of the songs on Double Fantasy were political.
And what war were they defending in 1980, and a few years AFTER the Church commision.
(By the way, the U.S. could have kicked Lennon out of the country in the early 70s, but they never did.)
I thought the theory was a bit off-the-wall, too.