I don't think the two [nail polish and assertive masculinity] are necessarily mutually exclusive.
The problem is more with people foisting their agenda on their kids, regardless of the agenda.
It seems like it is becoming increasingly popular to "encourage" boys to engage in traditionally feminine pasttimes, who haven't shown the slightest inclination to seek them out on their own.
There's a huge difference between giving your children the space and freedom to pursue their own interests, and vicariously living your own social agenda through them.
Sometimes it can be pretty difficult to delineate which is which, based on the media reports we get. My personal opinion is that if the parent allows their child [or a picture of the child that would make the child identifiable] to be shown in a news report, you can damned near bet the parents are pushing an agenda.
I have corresponded with a couple of bloggers who have sons with traditionally feminine interests. You don't see them on the news making a huge stink every time someone mistakes their son for their daughter because he's carrying a Barbie. Most don't even post pictures of their kid, or if they do, it's a picture with the face blurred or cropped out of the shot.
The failure to protect the child's identity in a lot of these "boy who likes x" stories makes it pretty obvious who, and what, they are really about.
Frankly, it seems like a lot of straight, white, upper middle class liberals trying to opt in on minority status by misrepresenting their sons as being gay. [All the while failing to realize what an incredible disservice they are doing to ACTUAL gay men, who don't appreciate being stereotyped as universally effeminate... but then, the far left has a longstanding tradition of actually ENFORCING the very prejudices they decry.]
Not only will their sons grow up to be straight [you can't *make* a kid gay], but probably with some pretty serious resentment at having been exploited and made a spectacle of.