I was in Walmart and had to steer my cart between another cart and a young woman who was standing on the opposite side of the aisle, absorbed in studying the label of an item in her hand. She started to take a step back, unaware that I was there, so I said "watch out" as a warning. She turned and gave me a condescending laugh and said "well, excuse me would've been a little better." So a warning of care turned into rudeness in her opinion. AITA for raising the alarm that way? I really thought my tone of voice was caring rather than admonishing.