I don’t think the OP is talking about those non-Catholics that do believe the Church remained but erred. He’s talking about those that don’t believe the Church existed for a certain amount of time. There are plenty of those around as well, and I too, don’t understand their reasoning.
If you have your own questions about Church error, I would suggest you start another thread on it. You’d be more likely to have your questions addressed there than on a thread that doesn’t address the concern you speak of.
A word of advice, though: if you phrase your question bittlerly or with anger implied, you’re not going to get very convincing answers, or have anyone bother to decently answer your question. Phrase them intelligently and neutrally if possible, showing that you are open to reflection on their answers. And probably the best place to post it is in the Apologetics section.
(Have you ever heard the phrase “you catch more flies with honey than vinegar”?)