In future, give it a good wash on the first clean, maybe go round 2 or 3 times.. explain to them that "it may" spot up or give white lines from the top frames.. this is just showing that the frames have not been cleaned properly or you have got water in the air vent, so try and steer clear of those..
Stop carrying you ladders on your car/van... it works well, because they dont see them they dont associate you with going up them anymore.. then only put them on when you need access, or have specific trad work to do - and insist they are for access and inspection only.
Make sure they know the benefits they are going to get from the use of WFP.. Sell it too them, and make them trust you.. transition is never easy whatever it may be in life - you just need to assure them and make them trust you.
If its a case of they dont like it.. stick to your guns, and politely advise you have stopped using ladders to provide a safer future for yourself and your family and decline their requests, even if it means you lose them.