I like your point here, and substantially agree. However in the interest of sparking a lively discussion on this topic (which I think is an interesting topic and worth discussing), I am going to play devil's advocate for a minute her.
In a way he is standing up for his freedoms/exercising them, at least in a weak easy way. He is voting with his feet (kind of like Amazon just did in North Carolina). Nominally if England (or any country) suffers severe brain drain among its highly educated (and hopefully highly productive, though he is posting on slashdot, so no guarantee's on that :) ) taxpayers, I mean citizens, I mean subjects, ah, call it whatever you want, that should sent a message to someone that their policies are disapproved of. It will probably go unheard, but it does at least hit send.
On the flip side, if all the people who cared enough about freedom to move to another country to secure it moved to a small list of countries that would, or at least should, give those countries a substantial population of people who care about freedom, and hopefully would be willing to protect it.
So while I agree with you that it is kind of the cop out answer to this problem, it is an answer of sorts, and is not completely invalid. I can see where he is coming from, the interests that fight against our freedoms are very entrenched and powerful, so it can feel futile. Don't let that stop you from trying though.