Why are men stigmatized for using sex dolls when girls use dildoes?

My girlfriends and I read an online article today about sexbots for men. The engineer-entrepreneur of the emergent technology said he wanted to offer something lifelike and responsive and satisfying to men who for whatever reasons couldn't attract mates. (Maybe you guys have heard of this community called MGTOW, in which men who chronically strike out with girls give each other support...) I was like, "That's an awesome idea!" But the room full of girls around me started heckling the article and any "guys who can't get real tail." Not confrontational by nature, I just listened to why they felt such prejudice towards guys they didn't even know. And the comments weren't good-natured play. They were downright hateful. Seems like they all think a guy's duty is to be able to entice and satisfy women, but that he shouldn't use toys himself. When I pointed out that we girls have been using dildoes for hundreds of years, they all said it wasn't the same, that a "real man" has game enough and stamina enough to get the "real job" done. (WTF??)

So can someone explain it to me? Why's it OK for girls to use artificial penises and vibrators to pleasure ourselves, but it's NOT OK for guys to use artificial vaginas or sex dolls to pleasure themselves?