The entire point of their door to door work is to convert people.
And they are so successful with that aren't they? What does that have to do with forcing NON-JW's from celebrating holidays? What school has been picketed by JW's insisting that the entire school stop the flag salute or stop celebrating holidays?
The point of a protest is not to force (which would not be "peaceful" and therefore illegal) but to convince and bring about change. His argument was that they do not try to convince. I demonstrated that they do. He was lying.
Regardless of their success rate, it doesn't stop them from going door to door in an effort to convince others of their cause and their rightness so that they join them. He was saying they do not do this at all, regardless of whether or not they succeed.