Ask Alice: Is It Reasonable to Insist My Guests Take Their Shoes Off?

Dear Alice, My apartment is all carpet, save for the kitchen, immediate entrance area, and bathroom. I'm very clean and always leave shoes or sandals at the tiled entrance and never walk on the carpet to keep it as clean as possible, especially now that I just got it deep cleaned/shampooed. For some reason, visitors and friends always argue over me asking them to not walk on my carpet with any footwear, despite knowing how hard I work to keep my apartment clean. I've been called "rude," "anal," ...