I'm going to have to disagree with you on that point... cards for some things, sure. Years ago, I was playing a match and got a yellow for "delay of game" because the ref said I stepped off of my line too quickly (I was a GK and the other team was given an indirect kick on edge of the 6-yard box). Something like that given to a 7-year-old, yeah... ridiculous. A 7-year-old will have trouble grasping what he/she has done.
On the other hand...what if a 7-year-old gets mad and hits another kid on the field? Blatant two-arms-extended shove? Dropped profanity (yes, I've heard it from 7-year-olds)?
Give the kid a yellow, let his/her coach talk to them and explain what the penalty was, and put them back out on the field. 7-year-olds aren't stupid - they are capable of understanding basic notions of having consequences to their actions.
However, we weren't given any details on what actually happened in this case, so I'm just going to have to remain undecided about whether Beckham was justified in my opinion.
