A) the idea that it might encourage others matters precisely jack-all. Your claim otherwise is like saying that you should have no right to free speech because someone else might use their own right to free speech to stir unrest. No shit Sherlock, the inability to prevent people from stirring unrest is why we have free speech in the first place. But let's say it did matter. The Catalans exercising self determination STILL means jack-all because it's completely irrelevant to anyone outside the EU (and the EU means the risks you're so worried about wouldn't be at play anyway). It doesn't do anything about the cost of secession in Africa, or Asia, or anywhere else. East Timor didn't spawn a global crisis as people threw off shackles. Neither did the break-up of Czechoslovakia. The breakup of Yugoslavia caused problems but they weren't global, they were in the former Yugoslavia. And let's face it, you don't give a rat's ass about redrawing borders because you weren't the least bit concerned about the Spanish demand for Gibraltar back with Brexit.
I didn't say that, I said law. It's what the law does that has value, not that it exists at all. And you plainly don't give a rat's ass about what the law is or what it does because you're only interested in maintaining the status quo BECAUSE it's the status quo. You sure as hell don't care about the law itself because as shown above, the law is irrelevant, it's whether a border might get redrawn and plunge the world into flame that matters.