They view the CC as the “Whore of Babylon”.
I would ask them who will be in heaven? More than likely, they’ll say the annointed class from their ranks. Ask how many are those? They’ll probably take you into Revelation 14, which shows a number, 144,000. Ask them, is the Lamb in verse 1 literal or symbolic? They’ll say symbolic. Then ask, is the Mt Zion literal or symbolic? Again, they’ll answer symbolic. Then ask will these ones literally have names written on their foreheads? …symbolic. Ask in verse 4, are these literal virgins being spoken about? Again, they’ll answer symbolic. Ask, in the same verse 4, are these 144,000 only males? They’ll say no. Then ask, then how is 144,000 a literal number amongst all this symbolism?
I would then ask if they could explain in John 6 why Christ promised eternal life only to those that ate of His flesh and drank of His blood, and ask them of they observe this in their religion? They’ll say yes, but only a small remnant of a literal 144,000 class eats the bread and drinks the wine. Ask, then does that mean that the others there will not have eteranl life if they don’t eat or drink? They’ll come up with some explanation of 2 hopes, for their believers, one earthly, ie a restored paradise earth and a heavenly class=144,000. So ask them to explain how the non 144,000 will attain this eteranl life promised by Christ if they don’t partake as Christ instructed? You’ll be able to take it from there…
If you reveal to them that you are Catholic, ask them, “Do you realize that you are going door to door with a Catholic book?” They’ll be taken aback and say, “What?” You=“You do realize that the Catholic Church canonized the bible that you are using, right?” They may know, they may not. If they don’t, they’ll deny it, and of you have sources, cite them. If they do already know, they’ll rationalize it away. Ask them, is it right for them to accept this canonization from the Catholic Church, when approx 60 years prior they officially defined the Trinity doctrine, a teaching they vehemently reject? Tell them that that would mean they are drinking milk from an apostatized cow.
Be charitable and pray, pray and pray. They are not the enemy, they are just seriously misled.