I was in the Philadelphia airport on a recent Saturday, and watched passengers go by. I formed a quick, but completely firm, opinion.
Men should never, never, wear flip flops.
Flip flops are for young girls.
What you do in the privacy of your own home is your own business, but do not wear those past your front door. Further, do not wear any sandals that expose your toes. Men's toes are generally ugly and disgusting. If you want to wear some Keen Sandals, which completely cover all of your toes, that is acceptable with shorts. Not with pants.
I've got that off my chest. I feel better.