...... From where I stand, they are walking examples of what it wrong in the martial arts, but their numbers seem to be rising due to the ease of getting slip shod instruction. Ask them, and they will say they are good. I disagree.
The joy of that though, as with people who exaggerate their skills, is that they either get found out or find out for themselves. The best way is to invite them to one of your training sessions where, without putting on anything special on for them hopefully they realise where they stand as far as training is concerned. It's a much easier way for them than finding out the hard way in a competition or even worse a brawl or street fight.