If the protestors are vandalising his business or refusing to leave his property they can rightfully be arrested but simply congregating in a park nearby is not an infringement on any right.
I wasn't aware they were preventing anyone from coming into the park. No person's right to use the park is any more valuable than another persons. A dog walker and a protestor have the same rights.
The police don't seem to be shy about arresting the protestors who are breaking the law. Breaking park rules are not law. I'm not going to deny that some people are acting like assholes, but don't generalize everyone protesting based on those who can't act responsibly.