Used to get this all the time twenty odd years ago. Seems to have died out round here now, there are so many window cleaners that nobody has a "patch" any more.
You can understand how someone can feel threatened if you are leafletting his customers but if I phoned up every WC that leafletted in my area I would never be off the phone.
I would just carry on, as I have said before this is business not the boy scouts.