The difference is that in mining bitcoin, you are a producer. When you accept rewards from Steem, you are a consumer. The rewards were produced long before you, I or haejin ever got here and if we left they would remain the same.
We all have a responsibility in deciding how those rewards are consumed. It is perfectly ok to downvote based on reward value. That is built into the design of steem to stop this exact scenario.
Jesus who are you
@moeknows