Huh... off-topic note: the fish is Jesus' sign, while the sandal is Brian's. Bet they knew that.
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Of course the fish is manlier, it's something you can slap people with, while you slip into a sandal. Basic cis-male logic. You're welcome.
Here's my proposal: the sandal is manlier if and ONLY IF it has a sock in it. Socks and sandals are typical for middle aged men after all, while fish are not. They're MANLY MEN so they only eat red meat and maybe some yummy, hormone-laden chicken. So that's absolutely crucial information for the future of masculinity. Is the sandal depicted with a sock or not?
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Of course the fish is manlier, it's something you can slap people with, while you slip into a sandal. Basic cis-male logic. You're welcome.