If any ideology guides them it would be a "myself-ology" if they catch you having ideas they don't have, they will downvote you. There's also the downvote bots, which put you on their lists for reasons that you don't always know. Never happened to me personally, but you can see these bots on some people's comment, they will just downvote because they have the power to do so.

This Post is quite right.
This one explains how to fight it

The simplest search on google gives lots of results of "flag war" like the ones I've put in in the example. steemcleaners is a "grey zone" and some are already thinking of doing downvote bots for after HF21... so meh, that's kind of scary to me.