Is what they have done perfectly legal?
Once the first argument has been overcome, the second one arises: what they do is legal, they say. But those who say this do not usually know the legal regime of responsibility of social networks regarding the contents of their users, neither in the United States, nor in Europe, nor in Spain. But it is true that they have heard of the governments around the world urging them to delete some of their content for years.
What they are not pointing out is that both the Communications Decency Act of 1996, in the US, and the Electronic Commerce Directive of 2000, in the European Union, and the Information Society Services Act of 2002 in Spain, only allow - and force - the deletion of clearly illegal content. (Although in the US they have wider understanding of what "objectionable content" involves).