There's no force involved here. The AMA is trying to offer the best deal, and if they can do that and make a dollar or two in the process then why not?
As for this being an abandonment of the AMA's purpose, I simply don't see it that way. No one is talking about shutting down competition, not advocating for hobbyist interests, or discontinuing the flying site or museum. The magazine isn't being dominated by drone articles. Geez, this is the organization that still keeps a bi-monthly article about CL Navy carrier a solid 35 years after CL flying in general had given way to RC as the mainstream control method of choice. The AMA is not an abandon your legacy type of institution.
However, if they don't pursue new revenue streams, they will have no choice but to stop some of those things. If partnering with a related insurance business helps shore up their income, then that's an act in the best interests of the hobby and the AMA's mission. I haven't seen a single concern in this thread that actually could become a reality that hurts the AMA. Congressmen seeing the ad and thinking the AMA is all about commercial use? Please. How stupid do you think congressmen are? Dropping aeromodeling concerns because commercial drone pilots become the most important source of revenue? Only if enough of them join to create a voting majority and they mobilize/organize and traditionalists refuse to co-exist with them. None of those aside from the last one is likely.
How about having a little faith in the leadership? They aren't perfect, but they got where they are by serving this hobby before they were able to make a job out of it. Why not expect them to be working for the organization's mission? For that matter, how about understanding that the EC has a more intimate knowledge of what the AMA needs than a hobbyist, a consumer who's never even attended one of their meetings? Why does the knee jerk reaction have to be doom and gloom and a wholesale condemnation of the whole AMA leadership at the tiniest sign of something new? That's the same mentality that is killing so many clubs; young pilots can do nothing to please the glow ARF crowd so they leave as fast as they came. I fear the AMA may go the same way, not because its leadership destroys it with harebrained schemes, but because its membership stifles adaptation to the changing market to the point that no one wants to be members after the current generation is gone.