The one difference with the other vaccines is that i DID research them before my children received them. They had all been around a fairly long time, and had extensive testing on them.... i was educated, knew what the potential side effects were, etc.
For me it isn't an issue of it falling under the purview of sex.... it isn't even so much the government regulation of it. Not sure i can explain it... but it feels wrong/dangerous to every parental instinct i have. This doesn't happen often but when it does i will do whatever i have to to protect my children from anything that produce those feelings in me...