Pedants are bad, but what is worse is a pedant who is wrong.
I remember being at Carlisle Railway station (of all places) once whilst waiting for a Railtour to come in that I was traveling on.
Anyway, I got talking to an enthusiast, and with no word of a lie, he corrected everything said.... all with the wrong pronouciation.
I caught on straight away and started saying things wrongly myself to see what he would do, and he just continued to 'incorrect me'.
I was just a bit bemused by him, but I now really do wish that I had corrected him, see what the idiot would have done.