In my province+ the nearby City there is a lot of activity \activism(?) of evangelical groups, and a surprisingly big number of mormon missionaries. They have their own living quarters\church, big enough to have a basketball pitch. And whats more normal I think, many JWs. they have daily stands in train stations, public parks, and weekly door-to-door activity. Should catholics try to preach (catholic faith) to them? Offer to dispel some myths, such as "idol worship"? Or is it better to just pass by and say a prayer keeping their faces in mind when calm at home? I almost feel as if all these religions are making a pincer attack upon a (formerly?) catholic country. of course they arent connected but.. they all are active.
JW's are really indoctrinated - they are almost cult like in my opinion. Three called at my door one day and fled when I confronted their beliefs and asked them when did their 'church' begin? It became a little heated actually and that's probably why they gave up as they knew they could not get to me.
I would say the answer to that question is how well one knows their faith. If you are so informed and filled with the holy spirit that you could even add to Scott Hahn books, go right ahead. But as many of these people in these cults started out as Catholics and were lead astray, I would say be silent. You are going to be debating with the devil here.... Sometimes I like to think of Jesus parable about the rich man : They had Moses and the prophets. If they did not believe Moses and the prophets then they will neither believe a man risen from the dead" In other words, they already had the Truth available and were still searching for something OTHER than the truth, and so were easily led astray....