I also disabled that one the moment it appeared, which was just recently.
There's nothing that can really be added to the opinion most people already have about MS and their deviousness, it just pays to try and be aware of what's part of an installed program, or in this case, a browser.
There's another plugin that's installed in Firefox without you knowing about it until you happen to check your add-ons, and that's a completely unnecessary iTunes plug-in.
My daughter uses iTunes, but we have no need for this at all, and didn't ask for it.

From various stuff I've read about the DRM plugins, it appears to be pointless uninstalling them, which is possible, but apparently they just turn up again.
I haven't tried that, but I could well believe it.