I...literally just explained my reasons why it wasn't a backfire.

1) he went there for political points. Stand in solidarity with people fighting for democracy, blah blah blah

2) he then gets his perfectly legal right to set foot in Zambia refused by government thugs, who want him to hand over his passport and cellphone

3) he comes back, gets to play the outraged defender of freedom and gets about 20x more press coverage than he would otherwise have hoped for.

It was a major political win for both him and the Zambian opposition, gift-wrapped by the Zambian government.