Dave
There are good and bad elements in all trades including window cleaning, if we all were swayed by the bad elements then you, I and all window cleaners wouldn't have any customers.
Door knocking can be a pain for house holders, I personally don't answer my door, but to completely ban something when there are alternatives seems over the top.
Also if you ban people going door to door will this include charities, the Girl Guilds, Boy scouts, political parties and all the other worthwhile people who come from your community.
What happens to you local Pizza,Indian,chinese and other small business who can't put leaflets though potential customers doors?
Would this ban also includes letters sent to potential customers, introducing yourself and you companys services?
If all of this type of advertising was banned and the only way you had left was to Yellow pages, how long before they see their advantage and increase their prices.
Dave you are allowed an opinion and you might have got a lot of work which didn't could from door to door knocking, but on the other hand there are thousands and thousands of window cleaners who do get their work from this method.
Instead of banning it. Look at ways it can be done in a more friendly manner, when I go door knocking I don't knock bungalows or houses that have signs on their doors saying No Canvassers Please, I do put my business card though their door though and I never canvass after 7 pm.