where is the thumbs down on mainstream social media ....

When a social media post can only be liked (*) it is left to "liking" negative comments to balance the view.

Commenting requires more effort (ie., being able to think and type) than simply clicking a "like" button.

Where meople can't be bothered to post a responsive comment the poster is either going to have ser post liked or ignored.

Being ignored gives no indication as to how many meople disliked the post.

That's just biased imo...

* (to be fair FB have introduced soft negatively connotated emojis - "sad" and "angry" - to imply dislike to soften the blow of opinion rejection)