The safer approach is proper cooking. Ground beef should reach an internal temperature of 160°F (71.1°C), checked with a food thermometer rather than judged only by color. Because grinding can distribute bacteria throughout the meat, the entire portion needs to reach the recommended temperature. Thorough cooking is far more effective than trying to rinse the surface.
Fat is a separate issue from food safety. If you want less grease, choose leaner ground beef or drain rendered fat after cooking. Some people rinse cooked meat to remove additional fat, but this may also reduce flavor, seasoning, and moisture. Large amounts of grease should not be poured down the sink because they can cool, solidify, and contribute to plumbing blockages.
Good food safety also includes keeping raw meat refrigerated, washing hands after handling it, cleaning utensils and surfaces, preventing cross-contamination, and storing leftovers properly. The simplest rule is to avoid washing raw ground beef, cook it thoroughly to 160°F (71.1°C), and drain excess fat safely afterward. Personal cooking preferences may differ, but basic food-safety practices should remain consistent.