Of course, there will be a small percentage of people fighting for "Yeerk rights." But I think their voices will be drowned out once people realize how delicious the McYeerk tastes.
Of course, those people could engage in acts of domestic terrorism like the Animal "Liberation" Front (added quotation marks) or the Animal Rights Militia. They burn down animal testing facilities and the like. Who's to say that there wouldn't be a similar miliant group for Yeerk rights?
I mean, granted Terran animals haven't tried to take over the world by enslaving humans (one could argue the reverse is true), but that doesn't mean that there wouldn't be a "People for thr Ethical Treatment of Yeerks" or something (presumably founded by someone who had never been infested and think they know everything, but just a stab in the dark).
Yes, the morphed Yeerks would face much discrimination, I think. And, if they were permitted to morph humans, they would probably live in an area.where no one else knew that they were morphed Yeerks, and keep that fact to themselves, closet the fact.