What he said. If you're lucky, you can get to the holes from behind and punch them out. Rarely that lucky though. A thin scraper behind the plate sometimes works, but doing that you always risk damaging the plate. You can drill the heads too, but then you need to source new twist pins.
I have managed to get two out by punching them so far from the back, with great difficulty at that. This won’t be possible for the others so ile try the pliers.
I tried pliers on the viceroy lathe I am renovating as I didn't do a complete nut and bolt restoration so couldn't get into some of the castings to push 'em out. This has worked for me before but the little tinkers wouldn't move on this on so I ended up just masking the plates off. Unfortunately, some of the paint pulled off the plates when I removed the masking tape so I would use card and blutack in future. Not too bad fortunately, better to take 'em off if you can.
I have some of these rivets that came with a load of other stuff I bought, dont think I will ever have a use for them so if anyone needs some pm me an address and I will stick some in an envelope.