Nike used Labor Day to roll out a 30th-anniversary “Just Do It” ad campaign featuring Colin Kaepernick. “Believe in something,” reads the Nike tagline. “Even if it means sacrificing everything.” Nike needs to rethink its tagline. The truth is, since the first day, the NFL take-a-knee demonstration has lacked a simple but critical piece to any revolutionary, culture-bending, time-tested protest. Personal sacrifice. Effective protestors accept that sacrifice and perhaps great personal loss are real possibilities…