I agree with you and most others, grind it back. I think there's more people out there that either don't understand welding fully or just don't know the proper way to fit tubing, but when i do car and motorcycle suspension and frame work, i know that some one's life may depend on those welds so i take every step i can to ensure nice thick walls (the best i can anyway) and make sure that the fit-up is snug enough that i can't slide the filler rod into the gaps before welding. And i even pre-heat all my materials after fit-up and before welding for extra "good measure". Plus when you're dealing with some very out of position welds where you can't reach the foot pedal and must use lift-arc this keeps you from having to run a high enough amperage to start the puddle on cold metal which usually ends up being a tad too much heat towards the end of the bead forcing you to work faster, so preheating does make it easier as well in some instances.