This needs to be stopped immediately!

I have been noticing this problem happening constantly lately. It needs to be stopped, it is out of hand.
The problem I am talking about is with the Downvoting on One Piece episodes.
Yesterday, Episode 1121 has a rating of 9.4, later in the day it had 9.2, and now it has 9.1.
When it was released, the episode has a rating of 9.8.
These people / bots that are giving the episode a 1 rating, just so it has a bad reputation on the episode. This episode deserves it 9.8 rating back. If there were professionals rating these episodes, they would give it a 9.8. 
You all need to make it not so easy to downvote anything. Make people have to write proper reviews like Rotten Tomatoes.

Here is the episode link:
https://www.imdb.com/title/tt33511832/?ref_=ttrt_ov

Please, and I am begging, sort this problem out. It has happened with most One Piece episodes and other TV Shows.