By what, banning plugins? Now you're asking the anti-DRM people to do exactly what they're angry at the pro-DRM people for doing: preventing people from running a particular kind of program on their computer. It's an incoherent position.

Not banning, simply not providing api for them.

That doesn't work. Look what happens with AV providers: they hack their own plugin interface into the browser, and everybody loses more security.

You can have arbitrary exceptions to ensure coherency. There is no reasonable need to have a position without exceptions. Reality isn't that simple.