I am not aware that Facebook has admitted to wiping out “Likes” on a facebook page. My deal is simple - innocent until proven guilty. A drop in “Like” stats does not have to be some conspiracy. It could be the people that really support impeachment already hit the Likes and it has topped out. There are many on the left, right and middle that do not support impeachment including many at this site. I am not one of them as I was calling for impeachment years ago regardless of what the Senate does. But even many die-hard conservatives are not interested in impeachment.
Regardless all you have is suspicion and not proof. Stats go up and down. To really find out you need someone on the inside. Good luck!