Unfortunately some units have entered the realm of folk myths and legends over their attitude to GA and transits.
One person gets refused gets wound up tells others, they then think well they aren't friendly I wont bother asking, they fly with someone else when asked why they didn't ask for transit tells the other oh they refuse transits and the myth escalates.
There are occasion when it simply isn't easy or possible to give transits, this can be for a variety of reasons. My Last unit was/is good at giving transits but I have read of an episode of recent when someone was refused and he started spreading the word of how bad they were at it, whereas we all know who work at the unit that 99% of the time they are given.
I would suggest if you are a regular flyer near any CAS and you are given the chance then visit the ATC unit, they will give you hints and tips as well as to how to best place yourself for a transit of the airspace.