Having someone cheer against you and your kid right next to you is what I believe causes the most issues. Not necessarily the sport, but where the spectators are.

Baseball parents that sit right behind home plate, or for some stupid reason sit on opposing teams side can be likely to have words

Football is typically other side of the field, so probably less so

Lacrosse and basketball, parents typically share one side of the field/court with no designated area so they are intermingled. Not good