If you have never seen it, the following video is from Penn Gillette, who is an atheist and no friend of Catholics (or Christians for that matter). He is part of the Penn and Teller duo who describe themselves as "eccentric magicians with a psychotic twist".
After a show, he had an encounter with a Christian man that he describes in this video. It is one of the most compelling cases I have ever seen as to why we should evangelize - and it comes from an atheist.
"If you believe that there's a heaven and hell and you believe people could be going to hell or not getting eternal life, or whatever, and you think that well it is not really worth telling them this, because it would make it socially awkward....How much do you have to hate someone to not proselytize (he means evangelize)? How much do you hate somebody to believe that everlasting life is possible and not tell them that? If I believe, beyond a shadow of a doubt, that a truck is come at you and you didn't believe it, and that truck is barreling down on you then there is a certain point where I tackle you and this is more important than that..."