No, there is a very real legal question about the level of force used in removing the protesters, completely aside from whether or not they had proper reason to do so.
No, the police is allowed to use reasonable force to have people to comply. Again, pepper spray is at the mildest end of applied force, well below tasers, rubber bullets or batons, which are also generally accepted methods of applying non-lethal force. Pepper spray is on par or even comes before physically handling a subject. Hence, pepper spray IS acceptable use of force, if use of force is necessary in general. You simply cannot apply any less force!
So, if the police have used reasonable force, the question becomes, have they enough justification to be using force in the first place?
Someone said there are "suspected deaths" where OC has been a part of. This is absolutely possible, pepper spray can trigger an asthma attack. Then again, there's also a risk of severe physical injury or even death when physically handling people. I seem to even recall one famous bass player, who died after being manhandled by a bouncer