If you think something is not worth an upvote, then don't upvote it. Seems totally fine to me. If you downvote someone solely because they post somewhere else, then you actively discourage them to post here. At least that's how I see it.
In regards to "my stake, my choice" - absolutely. We want to have and keep our choice of what to do with our stake. I guess the question is more about how we decide to exercise our choice that would be more beneficial.