Despite racing's inherent ordinal ranking, all runners, from sub-15 to "I walked every other telephone pole", are part of the same "class" when everyone is simply a "finisher" or "participant". When prize money is introduced into the equation, you now have two very distinct groups, those that paid to participate and those that walked away with the bacon. This makes the " participation class" incredibly uncomfortable because now their deficiency is implicitly recognized.
Liberals despise how this simple change challenges their world view. Not only must the opportunity be equal (which is impossible anyways in most races that start on anything close to a two lane road) but the outcome should be too (to make them feel better about their lack of ability, effort, and/or desire).
I'm generally ok with people harbouring this perspective - to each their own thoughts and feelings. But what the OP's example (and others that have told their own stories of backlash) is that it is not good enough to have one's own belief but that they must now *impose* those beliefs on the group.
Back to politics, I truly and generally don't mind people having liberal beliefs in their own lives - its when they have the audacity to start imposing those beliefs on the herd is when I begin to push back.