I mean, if you took some privates in BJJ for 5 months, just to learn some basic stuff, and drilled the hell out of it, is that enough?
Probably, yes. Unless you were going into a MMA fight, 6 months to 1 year of dedicated grappling defenses from a skilled grappler (such as a GJJ school), along with maintenance practice, is probably going to cover you in the vast majority of situations the average person is likely to see.
Let's play devils advocate. Technically if the stand up guy needs to know the ground, the ground guy should know some punching. I mean, just because one is skilled in the ground game, doesnt mean that they're always going to be able to take the other guy down. You mentioned something like this in a post to me. So, how much boxing should we have? 1 month? 1 yr?
Having done (and still doing) both striking and grappling, it's easier for a grappler to learn how to negate (or at least mitigate) most striking than for a striker to learn the basic skill required to mitigate most grappling. Heck, "cover up and crash to clinch, then work on takedown" is a pretty good, well proven, strategy that's way harder to learn how to beat than to learn how to do. Yeah, it can be beaten. But it's kinda like comparing a weapons to armor. The weapon is almost always easier to use and make than the armor required to stop it. That's the way crashing to clinch works. If you're lucky, you'll get in one strike as the person crashing in to clinch (while he's in a "cover up" position). Once he's got clinch he'll start working for the takedown. From that position you need to know how to stop the takedowns (which ain't easy) while either trying to strike effectively from clinch (which ain't easy) or forcing a disengage from the clinch (which is even harder). So, in this limited context, grappling proponents have it "right" (well, sorta).
So, yeah, strikers need to know some grappling and grapplers need to know some striking. But it's way easier to force a fight to grappling (and/or to the ground) than it is to force a fight to stay standing at at range. If the guy who prefers a striking game is much better trained and more skilled than the guy who wants to go to grappling, then he's got a better shot at keeping it in his preferred range.
You know what also forces grapplers to not crash guard to the clinch? A knife. Paradoxically, a knife also forces grappling. No one wants to get stabbed so a knife will typically force a person to stay out of range, which will be punching range or greater (depending on the knife). However, if the other guy is unarmed and, for whatever reason, has to deal with the guy with the knife, the only way to do it successfully is to gain control of the weapon bearing limb. I.E. "grappling."
And here's another spot were RBSD proponents has it right. Grapplers, just because you don't
see a knife doesn't mean he doesn't
have a knife. Season with other various weapons to taste.
This crap is way to complex and nuanced for many of the overly simplistic pronouncements I've seen in this thread.
Peace favor your sword,
Kirk