Not at all. You are free to say anything you like. What you are not free to do is STEAL the work of someone else and claim it as your own.
It says in your profile that you are a teacher. If a student turns in a paper that is a copy of a paper you have already graded with an "A", does that student also deserve an "A" because he found the paper, copied it and turned it in?
The same applies to posting on the internet. Do I deserve to be PAID for copying an article from CNN.com and calling it my own?
Sometimes, things end up being similar or perhaps too similar to the works of other people. Not everything is copied or stolen on purpose. Sometimes, they are happy little mistakes.