First, they are not familiar with the rules of the forum. You can read the link below.
Reading the rules of the forum is encouraged, but one does not need the forum rules to decide that plagiarism is wrong, it's drowned upon in writing and most people who do it, have a bad intent.
You can quote other people's information and indicate the source. But you must have your own independent opinion expression.
Not necessarily. Putting a link to the source would indemnify the user from any penalty, it is however suggested to have your own opinion and not just regurgitate other people's content.
Second, novices do not have a strong reserve of knowledge, so they cannot form their own opinions, and there is nothing to say. They must improve their cognitive level through a lot of reading.
Anyone can form an opinion, it does not have to be a correct one, that's the reason the community exists; to assist users in understanding more about Bitcoin. Read, understand, inquire, read some more and repeat.