Envy has existed far longer than social media, none of these things would go away if social media doesn't exist. Social media just amplifies it.
Comparison has always been the thief of joy.
This is just simply false. Every major study has shown that an increase in union membership decreases bigotry of all forms. They also show that Democrats win more votes in areas which increase the amount of people in unions, and lose elections when unionization drops (rust belt is a great example).
The causal link is also not difficult to understand, a union forces you to work together with your fellow workers of all backgrounds and makes it clear that your struggle is deeply connected to theirs. It allows people to see that all workers have a lot more in common beyond just the level of race, gender, sexuality, or religion.
Nobody is claiming it is an easy cure, but it is a very effective treatment.
Because there is no theory of quantum gravity we have no idea how gravity could interact with anti matter. By showing that antimatter behaves just like matter when interacting with gravity we can learn a lot about it and cut the number of possible theories of quantum gravity in half.