Yeah, Steem absolutely needs groups to get to the next level.
As you describe in your post, people will go to war against each other if they are forced to live in a same community. Fortunately this is just a technical problem so it can be solved quite easily. Let's give people a chance to create separate groups so they don't have to see every day people they don't like.
There are groups in Facebook and subreddits in Reddit. Currently tags can't be compared to subreddits because they lack important features, such as subscribing, and preventing unwanted users to post to them.
My solution to the problem is to create tags that can be owned: Feature proposal: Ownable tags
Owner of the tag can decide who can post using that tag. This effectively creates group function to Steem because it gives the owner a right to decide who belongs to the group and who doesn't.
This will also make the user experience much better. Currently I'm not using Steemit very actively because here is just too much noise.
I'd like to subscribe to topics, not users. It's hard to find consistently good content because authors don't usually stay with one particular topic (that I'm interested in). They write about lots of different topics and relatively big portion of their posts are not really that interesting.
The noise level would go significantly lower if I could subscribe to topics instead of users. That would make me use Steemit much more than I currently do.