I tend to think people who are against certain things often don't know why they are. For instance, the antivaxers may subconsciously think that we shouldn't have to do anything as evolution will sort it out eventually (causing lots of short term pain, but long term, I'd guess we'd save time/money not having to vaccinate everyone in that hypothetical future).
Similarly, people who are racist may simply not like the look of the other race from an aesthetic point of view, but because that's so hard to prove, they fool themselves and/or others into thinking the other race is 'inferior' due to other factors such as intelligence, wealth, crime rates etc. which are much easier factors to quantify and compare, (though still *really* tricky to get right in truth).