The Right to an Opinion
Means basically nothing. A “right” to an opinion just means you can hold it, not that it’s correct. To say “I am entitled to an opinion,” is a bit different because “entitled” might mean “earned,” as in “I have earned the right to this opinion.” The implication there is that the opinion is supported by facts, which it might not be.
Examples
“You have to respect my opinion!” No we don’t. In a democratic society, we can respect your right to express an opinion while still believing your opinion to be completely wrong.