Indeed. If a hypothetical blood boycott protesting these rules would do more harm, on balance, than alternative means of promoting public health policy reform, then giving blood is good thing to do, and our community should endorse giving blood — even though we might gnash our teeth at the apparent endorsement of discrimination or irrationality. We can clear our collective conscience, if need be, by explicitly noting that we think giving blood is a good idea even though there are problems with the way it is collected.

Similarly, if you want to donate a little money to a school in a poor community, and the only existing school teaches silly religious stuff in addition to valuable skills, you should probably still want to donate to that school.