It was a time-gated, 2 year ban. It wasn't lifted 'just because.'

During the period that they were banned, they formed a shell party, the National Socialist Freedom Movement, which won a stunning 6%, followed by 3% of the vote (In the two 1924 elections). After the ban was lifted, the next election was in 1928, where they won 2.8% of the vote. Much good that ban did them, eh?

I'm not sure how your point follows from the facts.

Point taken. The meta point still seems to stand though, which is that bans are ineffective.