Just because that stake has been removed doesn't mean someone else couldn't acquire a very large stake and power it up over time and do exactly the same thing. Sure it wouldn't be quick, but it would be possible, which is why the changes should be made.
Aside from that, why are we letting 20 people (actually 17 people) decide the direction of the entire project, not to mention safe guarding everyone's money. What if those 17 people get together and decide they don't like someone and fork their stake out? We've already seen it happen several times from both sides. So there is the security aspect for people's funds and why I also mentioned changing the consensus witness number to something much larger than 20 in my original comment.
Also, aside from an attack, there is the issue of a couple large holders being able to handpick all of the top 20 witnesses, which means the direction of the entire platform can be driven by a couple of the largest stake holders. Hardly a very decentralized model.
Not to mention that the current witnesses get entrenched in their positions over time as well, making it less and less likely they could ever lose their spot.