I have heard one cannot enter Canada from the US if they have had a DUI. Is this true?

I have a minor criminal record for a few stupid indiscretions as a teenager (trespassing, p.o.m., disorderly conduct, evading arrest, etc.) - no felonies. My first and only time in Canada, flying into B.C., I was detained at the airport after being belittled by some dumbass customs agent who repeatedly kept asking me where I was going to buy my drugs (no, I don't have dreadlocks, nor do I smell like patchouli). I was held in a little room for about two hours where I was repeatedly questioned about stuff that is no longer on my record (deferred to judication), and should be irrelevant. The customs agent questioning me said they had pulled my FBI file, and they knew everything about me. Eventually, they reluctantly let me through, but all in all a pretty f'ed up experience. This isn't just being unlucky, either - same thing happened to my brother and several friends of mine for petty past screw-ups. Maybe this is exclusive to B.C., as I've never been to Quebec or elsewhere. Shortly after this, customs agents at the B.C. airport tazed some helpless guy to death. Cops are all the same, Canada or anywhere else - just pigs with an axe to grind.