In general, our Western (not talking cowboy, btw) culture increasingly views a visible potential weapon as a indicator of potential mayhem. If there's nothing visible, there's no potential for mayhem, right?

Also worth keeping in mind, though a sgian dubh is generally quite small and approximates the folding pocket knife I carry on the strap of my gym bag (actually, the sgians I've seen are smaller), the mystique surrounding it seems to get in the way of common sense...so as Nighthawk and others have said, exercise your own common sense regarding its wear, as others' sensibilities may be lacking!

Leave the dirk at home unless you're on parade, reenacting, carving meat, etc...it's a weapon, and unless you're deployed, its purpose is poking holes in the wily Highland Haggis!

I suppose, if you thought you were being unfairly targeted for your sgian dubh, you could always try holding up a 7-11 with a brace of cattle, just to make a point...but I personally think it's easier to wear a sgian dubh only when particularly appropriate or acceptable (YMMV)...or just stick a pocket knife and bottle opener in your sporran, so as not to cause an untimely stampede of the two-legged cattle . I recall at one point in college I walked to karate practice carrying a bo, or maybe it was a jo, I don't remember...got a lotta static from the hippies, as I recall. I wasn't running around beating up phone booths like that guy from Police Academy, I was just a guy carrying a stick that looked like a weapon. It probably would've gone over better if I'd replaced the jo with a Louisville Slugger, see what I mean?

-Sean