ok, in bitcoin nodes anyone can be bad, but important that 51% will be honest. the same is here.
If few whales will be crazy it is nothing.

From other side do you know how much needed upvotes and SP to got your rep 69? I think you will be surprised. You need too much time, upvotes and SP to get reputation 69. Do you think nobody will see it?

Do not panic, It is hard to do and will take a lot of time.
Does not have any sence to see to one crazy whale, more important how much time needed to broke system and how much SP and people.

What you tell can be done only theoretically, as with bitcoin) It is still working.
But you are right - steem reputacion is not perfect)