Okay. You're characterizing this as "one zealot parent got butthurt". Without the tweet, I don't really have any context for what actually happened. I know I've been having this discussion with other parents and online since I got online in the early 90s.
At some toy sections, they are laid out as you say. And that's been the way to go for awhile now. Various toy stores have been doing this for awhile because they got tired of complaints in the stores of certain IPs being in a gendered area, as in My Little Pony in the Girls area or Power Rangers or Pokemon in the Boys area and kids not wanting to be conflicted like that.
But some toy stores still divy things up by gender and it does cause problems. Not just for Bronies (boys who like My Little Pony) or for girls who like Power Rangers, Pokemon, Marvel, DC, Ninja Turtles, etc. because that stuff is normally put in the boys section.
Did the company HAVE to cave? Of course not. No company caves over one tweet. That's absurd. If tweets had that power... rest assured, I'd wield it! I'd actually use my twitter, goldangit! However, like I said, this has been an ongoing discussion amongst parents for the better part of two decades. It's not just one tweet by one parent out of the blue.
Hell, my daughter is 21 and I purposefully stopped taking her into toy stores because the damned stereotyping was suffocating. All girls are pink and frilly. All boys are blue, green or red and masculine....on and on and on. None of the girl toys were thoughtful in the slightest. Most were dolls. It's like most "girl" toys were created to inculcate girls to only be moms. I was like WTF? Sorry. Wasn't having that. If that's what they wanted, great, but they were going to have a choice.
As for "princess Lego" stuff or kitchen toys... /sigh. You ever watch the Food Channel? There are boys and girls competing are making stuff that is pretty dang amazing. So why does EVERY kitchen toy have to be pink? Why should a boy feel bad if he wants to be the next Bobby Flay? Why should a girl feel "out of place" if she wants to be the next GI Joe? Gender oriented stores make kids feel "out of place" when they go to choose what they are truly interested in. And since it's not about taking the toys away, but about simply a different method of orientation that orients based on age and interest rather than gender (aren't we always saying "let them just be kids"), it seems pretty straightforward. And since they sell more doing it, seems pretty silly not to.
The point is that gender stereotyping is just dumb and that DOES hold girls back in real and quantifiable ways. Do some girls like the frilly princess stuff? Sure and there will NEVER be an end to that type of stuff. But, there are LOTS and LOTS of girls who can't stand that stuff and never liked it. Never...ever. But that's the larger issue. (and toys and clothes are different on many levels. That said, when it comes to IP clothes like t-shirts, pajamas, etc, kids want what they're interested in. It's easier for a girl to wear Power Ranger pajamas than a boy to wear My Pretty Pony pajamas for a number of reasons...but that's a different topic)
The direct issue is that stores sell MORE merchandise when they create gender neutral spaces focused around age ranges and various IPs like Lego, Pokemon, My Little Pony, Power Rangers, etc. If it took a tweet for Target or any store to understand that, then so be it. That it took this long for them to understand when so much market analysis has already BEEN DONE on this subject and objective market data is already available...well, then it's embarrassing for them that it took a tweet because they failed at selling stuff which is what they are in business to do.