Trying to convert people doesn't work. All you can do is pray and make sacrifices for them. And most importantly live a good, moral life.
While it's true that one can't convert people by argument, because it takes grace, it's somewhat of a cop-out to say that, as if Catholics should not be ready to at least defend the Faith by argument. Absolutely, pray & make sacrifices for conversions, and absolutely, live a good moral life to give the best example possible. But I do think it is good for Catholics to know some basic arguments so that when a non-Catholic says something against the Faith, I at least can do my best to show why they're wrong. Otherwise, I feel like I failed in my duty. Plus, if a non-Catholic uses some of their arguments against the Faith, and the weak Catholic doesn't know how to respond, there can be a temptation that,
hey, maybe they're right! [Or even for a 3rd party listener to think, well, the non-Catholic made more sense, and the Catholic had no good arguments.]
So, I think this is a worthwhile thread, even while I recognize that few people are going to be truly converted just by argument.