According to the Cambridge dictionary, to be "entitled" is "to feel that you have the right to do or have what you want without having to work for it or deserve it, just because of who you are". In the context of your sentence, it means that people have the right to have their own opinions. I'll list a few more examples. "Those kids are spoiled and entitled, but they're parents don't care." "Everyone is entitled to basic human rights." "Your employer is entitled to ask for your references." However,the word "entitled" can sometimes mean to give a title to a book or movie. "Margaret Atwood's latest collection of poetry, entitled 'Dearly' was released last year.

Its simply your point of view and everyone has their own view on different topics. So what is meant by the saying everyone is entitled to their own opinion is that you allowed to have your own view point on a specific topic and another person can have a different view point , even if you don't agree you got to respect it. As a English teacher we have debates all the time in a open classroom situation. one team will be for the topic and one team would be against the topic, the team who has more facts for or against would will the debate. Facts are things or points that can be proven. Hope that helped you a little bit.

have the rights