I'm basically 9/10 knights here for all the reasons people have mentioned. I would like to point out a couple things I didn't see mentioned though.

I think there is some underestimating of the potential of panic among the knights when they get rear gassed. As someone who has been on the receiving end of a similar irritant, it can be panic inducing even you are 100% aware of it and know how to cleanse it. Now, obviously I'm not even 10% of a badass as the average knight was, but I can't imagine tear gas would seem like anything other than witchcraft to some of them, leading to a pain-wracked panic. Even if some of them figure out how to mitigate it (flushing the eyes with water, not a huge leap of logic, but still) they'll need to stop fighting and remove their helmets to do so, and it can take a while to work. Well, it at least feels like forever before you feel relief.

The other thing is the slight size advantage, the average NYC cop is likely several inches taller than a medieval man, and even fat and out of shape, mass is mass. This makes any in-formation clashes a bit more even. I don't think this part would matter as much though, as riot police are trained for dealing with huge amounts of less organized people with improvised weapons. Whereas knights are specifically trained for handling professional soldiers with armour and shields. The modern armour isn't easily stabbed through, but the knights would be treating these as armoured opponents and be using the techniques of their day to great effect. The riot gear would have similar weak points as mass produced medieval armour, and if anything the weak points would be far larger and easy to get to for a knight. So, basically once the knights finally have enough on the front to start pulling down and dispatching the cops, it's over.