I don't get it either... It's like calling a lawyer because Google links to your page.
No, in this specific case, they are sending images from the page to users, bypassing the actual page.
For a site where the user value was in the image and the monetization was elsewhere on the page, it's capturing the value of your work and bypassing the mechanism which pays you for that work. It may be legal, but even if so it is not sustainable.