But downvotes for disagreeing with content
This means steemit is suggesting you should downvote everything you disagree with, regardless of it being good, legit content or not. I.e. my comment above.
Disagreement on rewards
This means you don't think the person should get the reward. Even if you disagree with an author's post by a matter of opinion, that doesn't mean you disagree they should get that post's rewards.
There is a lot of difference. You should downvote spam because spam shouldn't get rewarded (1st sentence), but you shouldn't downvote a legit opinion merely because yours is different (2nd sentence).
I never disagreed with what you're trying to say, but how you've written it, as some people may end up misinterpreting you, which would be awful.
Every upvote is appreciated, no matter how small or big. If you see anything you like on my channel or maybe on @gamegiveaways, please do upvote it. Thank you.