It is ideological, not logical in my opinion.
And what Mozilla should do right now is rather reemploy the servo team(and more), to actually build a innovative browser again.
I agree Mozilla should be building browsers, supporting open source and being active on the committees.
But I wouldn't choose DRM as the hill to die on. There's probably better examples of things Mozilla did wrong.
I do get the ideological objection to not wanting to support DRM, although I don't think that's the battle that Mozilla should pick right now. But extra clicks probably wouldn't make anybody who does happy, while inconveniencing most other users.