Downvoting is indeed a major aspect of Relevant which has been of concern to many, as I have read interesting topics/discussions and funny ones too, about it.
I've read posts where people suggested that reasons should be demanded from a person who is downvoting before the downvote will go through.
What I have learnt, which I strongly believe too, is that different people have different reasons and everyone has a right to theirs. By implication, all the reasons you stated above are valid, and even more.
If everyone is allowed to downvote whatever they feel like downvoting for whatever reason, even if they are wrong reasons, then there is a serious concern. People could downvote for shear hatred.
And that is why the concept of Reputation comes in - people whose opinion align with the objective of a community are admins of each community and they have high reputations. These admins observe contributions of other community members and upvote comments that rightly represent the interest of the community, thereby increasing the reputation of such members who make such comments. Then there will be admins and high reputation members who, to a greater degree, without bias represent the interest of the community.
So if someone has a wrong reason, he/she will probably not rise in reputation and a downvote from such will have little or no effect.
I have seen believes/religions/interests play a role in people's downvoting decisions too. Posts about LGBT+ and laws around them make news and fit into News Feed community but some people find such offensive. There was once a post around that and someone commented with a contrary opinion based on his/her believe, the comment was downvoted.
It is an aspect that cannot be wholly summed up, but if you ask me, I'd say a good check has been put in place.