If somebody tells me "you are wrong" i take it personally. If they tell me "this looks wrong" and explains why, they are not criticising me but my work, which might truly have been wrong.
It's the difference between "you" and "it" being wrong, where only one of those is objective.
Another nice example:
"I'm so sorry, but this looks stupid"
Vs.
"I'm so sorry, but you're being stupid"