People are free to tell others not to patronize a certain business or activity. That's what advertising is. That's what boycotts are. Pro-lifers are in front of the abortion clinic property to exercise their constitutional rights - to peaceably assemble and protest abortion; to inform the passing public about the nature of abortion; to inform the incoming women about abortion.If that's all Scheidler et al were doing, your statement would be correct.
Deliberately seeking to physically prevent people from entering of their free will is another issue entirely. Attempt to impede me from going about my lawful business by means of false arrest, and you will not like my reaction.