You haven't really played devils advocate, you've just suggested a completely straightforward example that demonstrates why we'd rather not have the pictures as part of the hiring process.
Are you suggesting the employer never sees your face? This response makes no sense. They will see you at some point in the process regardless of whether it's on linkedin or in person at the interview. Physical appearance is part of life, it's no more discriminatory than refusing to hire stupid or mentally deficient people.
I'm suggesting that if our goal is to hire people based on their merits we should limit the extent that well understood bias influences the process.