My answer is no, instead style can be expressed by our masculinity and applied to items even if the items is gender specific.  Hello Kitty or My Little Pony is not changing masculinity but we change Hello Kitty and MLP to fit our or in spite of our masculinity.

I been thinking both is late as I am creating a Hello Kitty panel for a convention. I am a guy who been interested in Sanrio / Hello Kitty as a way to express my Fury culture interest. It is a in a way backlash to what I see as sameness of furry media. Most furry media is ether toony flat badge art or gay/straight twenty something with angst or relationship problems. I see Hello Kitty as something different way as a way to express my furriness but not supporting the noting of gender neutrality. I have recently started watching My Little Pony Friendship is Magic and like other guys and like the show. I do not see Hello Kitty or My Little Pony change the notion of gender differences but how style and taste is incorporated and express through our gender difference and even bypasses them. I like girly Hello Kitty items but I am not gay or transgendered, I am simple put personal taste, individual expression, and nonconformity above my own male gender nature.

One item I need to address; my liking of Hello Kitty Girly or not is not an endorsement of   militant feminist notion of gender neutrality. Boys are going to be boys and Girls will be girls. One way I seen how gender differences is played out is two online communities:  Hello Kitty Junkies and Equestria daily.  Hello Kitty Junkies is dominantly female 6000+ women vs. 125 men. Much of the focus is on acquiring items and shopping. While I enjoy the site I can note the difference of interest between me and female members. I would make new group reporting news about Hello Kitty or pictures from various conventions and not receiving very much response, yet pictures of my acquisitions do.   On the other side is the Bony site  Equstria daily which  is mostly male,  and focus is much more different  and broad mainly on the My  Little  Pony  through news, analysis, art, stories, and crafting.  I think the difference between the sexes is why a bunch of guys who like My Little Pony can create an event like Bronycon and attract thousands yet except for a few events The Hello Kitty Convention could not get off the ground in 2008. Do women prefer a trip to the boutique with a small group of intimate friends vs. men by the thousands get together at a Football game? Now substitute   Brony Con for football you get the same thing.  

We men  are not becoming less or redefining masculinity by liking My Little Pony or Hello Kitty but realizing as men can separate masculinity from aesthetics, style and personal taste.