People do think they can win. I do not consider the Taliban a terrorist group, but they were irregular forces that fought a war, and they won, in a limited sense. The IRA won, in a sense, both with the creation of the Free State and with the end of the Troubles. Mandela won, although the ANC was designated as a terrorist organization. Vietnam won.

The Black Panthers were an actual threat to the racist institutions in the US. The Weathermen were not. The Panthers had a strategy. The Weathermen were angry college students without training.