The "right of corporations to speak" is just the right of people to speak when organized into a group. The ACLU is a corporation. A union is a corporation. The essence of that decision was that when a bunch of individuals (who all individually have the right to speak) get together in a group and set up some rules, they don't by virtue of that fact lose the right to speak. It doesn't mean "corporations are people" except in the sense that corporations consist of people.

(It's also worth noting that the vast majority of the recent nonsense over abortion has entirely to do with the last trimester. The fact that something is a "strongly held right" doesn't mean some people won't from time to time argue it should be modified or changed. That's just healthy political debate.)