The red X was overkill in image to simply denote a disagreement, It was a poor choice for that message IMO, another color might have toned it down enough, like orange or yellow maybe, and "X" is also a bit much. A simple universal slash/diagonal would get the same point across without the cancel aspect. It's useful, but it's like as I have stated before, like using a 2lb sledge when all you need is a 12oz ball peen.