A lot of things suck right now. Social media definitely give us the ability to see that. Using your personal ideology to link correlations is not the same thing as finding causation.
There will be undoubtedly be some damaging aspects of social media, simply because it is large and complex. It would be highly unlikely that all those factors always aligned in the direction of good.
All too often a collection of cherry picked studies are presented in books targeting the worried public. It can build a public opinion that is at odds with the data. Some people write books just to express their ideas. Others like Jonathan Haidt seem to think that putting their efforts into convincing as many people as possible of their ideology is preferable to putting effort into demonstrating that their ideas are true. There is this growing notion that perception is reality, convince enough people and it is true.
I am prepared to accept aspects of social media are bad. Clearly identify why and how and perhaps we can make progress addressing each thing. Declaring it's all bad acts as a deterrent to removing faults. I become very sceptical when many disparate threads of the same thing seem to coincidentally turn out to be bad. That suggests either there is an underlying reason that has been left unstated and unproven or the information I have been presented with is selective.