I morally support both protests, but agree that a 'march away/boycott' protest would have a greater impact than a 'march to/attend' protest. (if both were of the same scale and thus comparable on a like-for-like basis)
FWIW, I think it was a shame that the thread starter felt it necessary to include an opinion on what protest was best as it set the scene for the tone of the thread thereafter.
A simple declaration that both protests are complimentary would have been less contentious opening post IMHO