Many of us develop our politics online before and whilst we organise in person. That was the case for me, and if it were not for all the online discussions I participated in and read I don't think my views would be as developed as they are now. It loosened me up for views that were being presented to me in person and made me aware if an entierely different universe of discourse. Posting does serve a propagandistic function in a kind of low-grade, stochastic way; people dont change their mind with a single argument but after a position has been normalised to the point that they begin to seriously consider it and its merits. I also believe having a correct theory is necessary for good political action, which is the definition of praxis.