Joseph Smith, the founder of Mormonism, may not have been Catholic, but he certainly made some very interesting points, which can easily be used as apologetics for the true Church.
From a sermon on 16 June 1844 (found in The New Mormon Challenge, p. 41):
“The old Catholic church traditions are worth more than all you have said. Here is a principle of logic that most men have no more sense that to adopt. I will illustrate it by an old apple tree. Here jumps off a branch and says, I am the true tree, and you are corrupt. If the whole tree is corrupt, are not its branches corrupt? If the Catholic religion is a false religion, how can any true religion come out of it? If the Catholic church is bad, how can any good thing come out of it? The character of the old churches have always been slandered by all apostates since the world began…”
From JS-History 1:9-10 (Pearl of Great Price):
“My mind at times was greatly excited, the cry and tumult were so great and incessant. The Presbyterians were most decided against the Baptists and Methodists, and used all the powers of both reason and sophistry to prove their errors, or, at least, to make the people think they were in error. On the other hand, the Baptists and Methodists in their turn were equally zealous in endeavoring to establish their own tenets and disprove all others. In the midst of this war of words and tumult of opinions, I often said to myself: What is to be done? Who of all these parties are right; or, are they all wrong together? If any one of them be right, which is it, and how shall I know it?”
Notable, too, is a story from Orson F. Whitney, recounted in A Marvelous Work and a Wonder (p. 3-4), a top Mormon apologetic book:
“Many years ago a learned man, a member of the Roman Catholic Church, came to Utah and spoke from the stand of the Salt Lake Tabernacle. I became well-acquainted with him, and we conversed freely and frankly. A great scholar, with perhaps a dozen languages at his tongue’s end, he seemed to know all about theology, law, literature, science and philosophy. One day he said to me: ‘You Mormons are all ignoramuses. You don’t even know the strength of your own position. It is so strong that there is only one other tenable in the whole Christian world, and that is the position of the Catholic Church. The issue is between Catholicism and Mormonism. If we are right, you are wrong; if you are right, we are wrong; and that’s all there is to it. The Protestants haven’t a leg to stand on. For, if we are wrong, they are wrong with us, since they were a part of us and went out from us; while if we are right, they are apostates whom we cut off long ago. If we have the apostolic succession from St. Peter, as we claim, there is no need of Joseph Smith and Mormonism; but if we have not that succession, then such a man as Joseph Smith was necessary, and Mormonism’s attitude is the only consistent one. It is either the perpetuation of the gospel from ancient times, or the restoration of the gospel in latter days.'”
Mormons should take this into account.