i don't think she meant that pink/purple = dumbed down.
i think she meant that they made the pink/purple sets
less complex to build = dumbed down.
which sends the subtle message 'because you are a girl and like pink and purple you must not be that smart or capable of complicated spacial building tasks'
so, if
lego added sets that featured characters/colors generally considered 'girly' but maintained the same level of complexity as the current sets that would probably be less controversial.
or maybe the sets in the current lego friends collection could have include more advanced sets in addition to the current offerings.
my dd is turning 4 this week and is in a decidedly pink and sparkly phase. so i like the idea of lego sets for children (regardless of gender) who are into pink and sparkly things. but those sets should have the same level of (age-appropriate) complexity as the more 'neutral' or 'boy' sets.
i agree with your point "what child wants to play with a dumbed down toy?"
i don't so much mind there being a couple of 'remedial' sets in any collection, regardless of theming. the lego website is acting up for me so i can't confirm if there are some in all their current sets. but there should be an equality of complexity, regardless of the target demographic.
the problem is, children don't necessarily think critically about the toys they are presented (i'm sure some do, but most just want to play) so it's our job as the grown ups to think critically about the toys that our kids are presented with.
so probably, just as many girls would be attracted to the lego friends sets if they contained more complex building tasks. but they aren't given that option.
sorry that was rambly. i'm sure this will have been discussed by the time i hit post.