I've never heard anyone say that
I've spend decades living with Polish people and the same living with British people and I have never heard anybody say that the word 'Pole' is remotely derogatory or that it is supposed to be derogatory or that it is used in derogatory ways.
The term "Pole" is derogatory to me and many other Polish people I know
Clearly you don't know many Poles. I refer you to
the Federation of Poles in Great Britain (ht tp://zpwb.org.uk/index.php/default) and
the British Poles Initiative (ht tp://britishpoles.uk/).
Even Poles who get very butthurt about British people have no problem with the word: theguardian.com/commentisfree/2015/aug/17/polish-downing-tools-get-recognition-deserve-state-handouts
I am referring to how Polish people and I, as a Polish person myself, may find such word offensive even if it was not intended to offend.
Perhaps the way you get upset by a word which Polish people are very clearly more than willing to use to describe themselves says something about how Polish you are?