Lenin’s point in What Is To Be Done? was that there is no middle ground between revolutionary socialism and liberalism! Any de-emphasis of Marxist theory strengthens bourgeois ideology by default. What makes this dangerous is that the party, functionally, absorbs the energy of dedicated, loyal people who want to be revolutionaries and channels it into work that never actually threatens power, abandoning the necessary and patient work of developing leadership prepared to support the working class in times of crisis.
Resignation letter of a [now-former] member of the PSL
It is just really hard to get one’s head around people who know what they are doing is pure evil, and not only doing it anyway, but also reveling in it.