If an instructor, or a flying school, cannot take a request from you to fly with or not fly with an instructor without taking it personally or making you feel guilty or demanding an explaination then they don't deserve your hard-earned. Or anyone elses.
Simple.
If you were to give up flying because of an instructor like this then he/she ought to have their licence revoked.
And if the school hasn't picked up the fact that an instructor can't deal with this sort of thing or that they are trying desperately to keep you in his/her little group so they don't lose flight pay, then the owners or Management ought to collectively have AFEs entire stock of kneeboards shoved up where the sun don't shine.
When will people who work in a, let me remind you, LEISURE industry, (you know, where people spend a lot of their leisure time and money), stop bitching or feeling hard done by because they chose to commit to a career where they know there is little pay or getting all elitist and looking down on the people who pay their wages and remember they get to fly for free and have the smell of Avgas in their nostrils all day and stop being so bloody short-sighted.
Not that this is a particularly emotive subject for me, you understand.