Those extra chords are diminisheds, which are DEGENERATE, SICK and EVIL. They lead to divorce, drug abuse and teenage pregnancy. They need to be STAMPED OUT forthwith and people who play them are to be SHUNNED.

At least, that was the idea the Scottish programming department of the BBC had in the Fifties - dance bands were forbidden to use them on-air.   That eventually changed thanks to the deviousness of Angus Fitchet, who liked adding manouche jazz chords to his arrangements and wasn't going to let Lord Reith stop him. So he wrote a tune, "J.B. Milne", which has a prominent descending diminished seventh arpeggio for which no other harmonization makes sense. It became one of the most popular tunes of the period.