If you are truly convinced that there is some solution to all human problems, that one can conceive an ideal society which men can reach if only they do what is necessary to attain it, then you and your followers must believe that no price can be too high to pay in order to open the gates of such a paradise. Only the stupid and malevolent will resist once certain simple truths are put to them. Those who resist must be persuaded; if they cannot be persuaded, laws must be passed to restrain them; if that does not work, then coercion, if need be violence, will inevitably have to be used—if necessary, terror, slaughter. Lenin believed this after reading Das Kapital, and consistently taught that if a just, peaceful, happy, free, virtuous society could be created by the means he advocated, then the end justified any methods that needed to be used, literally any.(Link)
For abundant proof: Here. And here.
Or just wade through the merde that is any comment thread on any progressive blog.