Geoff,

My Latin is so far from me that I did a search on google about non sequitur
www.gcse.com/english/non_sequitur.htm

It's fits perfectfy the guy you're =>

people who think they're clever use this far too frequently.
And the other part lets me a bit perplex =>
is sometimes used to indicate that an illogical conclusion has been made from something!
Concluding that I wasn't logical let me hope that you'll bring some arguments that prove it!