If you were to publish neutral research showing that, were the US were to draft all men 18-35, then the US armed forces would grow by X% and we could fight Y major wars at once while occupying Z square miles of foreign territory, then it would seem mostly senseless to direct anger or criticism at you if your claims were factually sensible.
If on the other hand, though, you were to promote the idea that the draft was needed, that it would produce a socially useful outcome, and that people who oppose your view are being irrational and selfish, then you've entered into a moral debate.
And further, if you own a large defense contracting firm, then your claims and your moral position about the necessity of forcing people to join the military would be subjected to additional, admittedly ad hominem, scrutiny.
Instead I analogize with drunk driving -- significantly fewere drunk drivers equates to significantly fewer 3rd party injuries and deaths as a result of drunk drivers. Similarly in the vaccination case, there are 3rd parties who stand to suffer from the actions of those who do not receive vaccines.
Edit: I forgot to put my second point, which is:
I agree with your analogy in that those who stand to benefit should be closely scrutinized when advocating a position.