Yes, it's true that people are more likely to say they don't really know what they're talking about when discussing law. This seems like a fine thing to me and I wish people would do it more for other subjects.

A large part of what people say on the Internet is confident and wrong. For any hot topic, people will pretend to be experts after reading a news article or two. It's not uncommon to have debates where nobody in the conversation has any relevant experience.

If people were more realistic about what they know about the world, I think conversation would be a lot more realistic and less heated. (Yes, this is very unlikely.)