It’s not fair to say in a blanket manner that non-Catholics will try to convert Catholics. It’s also important to distinguish between two things:
- The attempt to convert Catholics in the belief that they are “not Christians,” and
- The normal process that goes on in Protestant churches of trying to get visitors and friends to join their church. Generally the more moderate and sensible pastors will make a point of not trying to recruit someone who already has a “church home,” but you will always find the over-zealous folks who try to persuade any visitor to join.
In many evangelical churches, very much including the Nazarenes, most people are going to fall somewhere in between the two. That is to say, most people in such churches will say that Catholics “can be Christians,” but will not assume that all Catholics are. This is reasonable given their definition of “Christian,” which means “having a personal relationship with Christ.” Essentially this corresponds to being in a state of grace, but unfortunately many conservative evangelicals identify it with certain language about conversion and the basis on which one expects to go to heaven.
In other words, while I’d hope that most Nazarenes wouldn’t assume from the start that Catholics are “not Christians” (I’m sure some would, though), if they ask if you are “saved” or “going to heaven” and you give them some sort of conditional answer (as most Catholics would), they may decide that you need to be “saved.”
On the other hand, as an ecumenical Protestant I’m all in favor of people from one church participating in activities at another. I think this is very important to what the Pope has called “spiritual ecumenism.” So I’d encourage you to go ahead, but be ready to express your faith in terms that will make sense to evangelicals. Stress the fact that your hope for salvation is in Jesus Christ and that you are a Catholic because the Catholic Church has taught you to know and love Christ. If you emphasize this (rather than making it sound like “being Catholic” is an end in itself) there’s at least some chance that the Nazarenes will accept your Catholic identity and desire for fellowship and not see you as a potential convert. Perhaps you can even overturn some of their prejudices.
In Christ,
Edwin