It's a pretty big deal. When everything starts at urgent and gets worse from there, people will just rescale the noise to be more understandable. It's just like the joke about sitting down and assigning points to a task and finding out everything is 100 or all bugs are critical or all tasks are top priority.

The meta joke here is that is some ways every security issue is critical, but if everyone is immune to the fear then escalation will feel like the only choice. Either you slowly discharge that stress immunity by being sensibly mellow, or you start packing heat to 'convince' everyone to reboot NOW. (There's probably room for some amount of finesse between these two extremes.)

EDIT: There's two terrible responses that seem to come out of this. Either no one gives a damn, or no one gives a damn and just does whatever you say. The first is bad because nothing gets fixed, and the second is bad for `red_admiral's reasons (users treat anything that looks like a security rant as a EULA and just do whatever it says).