How better to be ambassadors for our faith than to lead by our words, actions, and examples? If we aren't physically present to those who are unbelievers, where will they witness's this behaviour? Isn't it by being among unbelievers that they have the opportunity to learn? Then, as they observe our sincerity in our faith, they will come with questions and be open to the Word. Even Jesus ate with tax collectors because he wanted the Word to reach everyone. If we hide ourselves from those who need us to show the way, how will unbelievers ever find their way? This does not imply doing what they are doing - it is quite the opposite. It is setting an example without being judgmental, and in my own personal experience it is the most powerful form of evangelism - an evangelism that leads by example.