I'll argue for two different options:
Vote based on rather you agree or disagree with the post and do not show user reputation.
There's a (relatively) small amount of topics that have an objective right or wrong answer. Most topics (such as this one) have many options and well argued alternatives can provide a positive contribution to the discussion even if they are not in line with the popular opinion. As such, the "reputation" of each user would reflect over the posts they've made on topics where people could be bothered to vote, whether they are with or against the popular opinion. This is not a very interesting metric in my opinion. I'd also say "reputation" is a rather misleading name for it.
Vote based on rather the post is in good form and do show user reputation.
Another alternative is to vote based on rather the post is a good addition to the topic (or a solid topic start). For example, a well argued point you disagree with would be +1. An unexplained statement you agree with might be -1. This would make the reputation for each user the overall contributions they've made in their posts. You do not have a measure of popular support for options. Instead, you perform discussions based on the quality of the arguments. Then, if you do want a quantitative measure of the community support you could open a poll.