"Everyone is entitled to their own opinion!"
Yes, and you are also entitled to commit suicide by drinking Drano, too. So? Why yap about it?
When someone declares their entitlement to an opinion, you can be certain they are aware on some level that their opinion is wrong. They instinctively know their opinion has been weighed by reality and has been found wanting. They may not be willing to admit it, and may be desperately trying to carve out a safe space for their sad little flawed opinion with this classic gem.
An example (one of many*) of this is when an anti-libertarian is confronted with objective facts showing that there can be no such thing as a "good cop". They really don't like this one, and will unfailingly try to save face by whipping out their entitlement to an opinion.
Yes, they can hold the opinion that there are "good cops", but reality shows otherwise. Sure, there can be nice cops, just as there can be nice Mafioso, nice rapists, nice burglars, and nice murderers (at least when they aren't committing the acts which define them). But by being any one of those, including a cop, they eliminate any possibility of being a good person.
When this is pointed out, the "everyone is entitled to their own opinion" is one last desperate shot at trying to not look like an whining ethical weakling.
It never works.
*I also see it a lot with anti-gun bigots and "taxation" advocates. Like I say, basically anti-liberty bigots of all stripes who come to realize they can't support their flawed opinion when measured against reality.