You guys are both arguing right by each other.
Turk is right that as a civilian I can't know, at the time, whether or not the police had probably cause to arrest/search/detain me. However, after the fact, the answer can become clear. By adding harsher penalties and punishing police who violate citizens rights, we can eliminate a lot of this behavior because police will fear repercussions just as citizens do.
So if it turns out this guy wasn't doing anything illegal at the time he is searched and arrested, the officer should get an unpaid suspension or something similar.