Well, I have mixed opinions on this one.
To be honest, right now we're facing a situation where the gaming industry is under pressure for there not being enough attention paid to enforcing ratings. There is even a case before The Supreme Court over this one. If EA just knowingly let kids get access to these kinds of games, that's a big issue.
Now, one thing I will point out though is that while a lot can be said about parental responsibility, and parental rights, there are things parents can't do with their children. While rarely enforced, technically the "PG" rating stands for "Parental Guidance" which means that parents have the choice, and are supposed to accompany their child (or give direct approval on the spot). In the case of an "R" rating, that means restricted and that even with parental approval kids are not supposed to be admitted to those movies, the same applies to an "X" rating. In nasty divorce cases and the like one parent allowing a minor to watch "R" rated movies has been used as a hammer for this reason, since technically it's negligent behavior. In cases where an adult accompanies a kid into an X-rated movie, we're getting to the "Child Services" level.
With the industry under the pressure it's facing now, the last thing that EA needs is for someone to have examples of them giving kids access to "M" rated games which are akin to the "R" rating when they technically aren't supposed to, even with parental permission.
Ratings are tricky because they aren't set by the goverment, there really isn't a way of arresting someone for violating ratings, which is exactly what the whole supreme court case is about. This is also why most theaters aren't going to make a big deal if some kid goes to an "R" rated movie accompanied by their parents. If the parents are there, nobody is going to make the complaint. The game industry however is currently under a microscope, and it doesn't have to just worry about the parents right now.
I'll also say that the parent in question probably shot himself in the foot when he went public with this. I'm not sure when he actually started complaining in a public sense. See, with what is going on EA backing down could be held against the ratings system. The more people aware of the situation (and there are people looking for just this kind of thing right now) the better the chance it will be used someplace EA wouldn't want it to be mentioned.
All told, I am not a huge fan of EA's business practices, but at the same time I can't fault them for this right now.
EA needs to get itself organized however, truthfully this might be the right thing to do, but it's both surprising and hypocritical coming from the same company that came up with that "Dead Space 2" ad campaign. Of course then again, now that it's become fairly public, I suppose EA can take this case as a counterpoint if officially challenged, so they can say "we are very strict in enforcing the ratings, that Ad campaign was *JUST* an Ad campaign, even if it was ill conceived we *obviously* do not condone minors getting "M" rated games under any circumstances... even if an obviously negligent parent gives permission".