I just got a chance to see Sister Beck's now infamous talk at General Conference a week and a half ago.
Let's get a couple of preliminary things out of the way first.
1. I really appreciate that she did not use the "Relief Society voice." (TM- the Church of Jesus Christ of Latter-day Saints)
2. As my wife pointed out to me, if women felt like Sis. Beck was being hard on them, there was some justice in this. The men get at least two meetings a year where we get told what a bunch of lazy, porn-addicted louts we are. The women can get a stern talking to now and again as well. You'll be fine.
3. It is somewhat insensitive to speak just to the mothers. This is one of the broadest and biggest dilemmas in the Church today- how to teach the eternal principles of the Gospel when facing a room full of people for whom some portions of the counsel may not be presently applicable. If Sis. Beck failed to speak to single women, married women without children, etc., this fault is definitely not unique to her. The same unfortunate mistake is carried out by plenty of teachers and speakers in Church settings each week.
Now to the meat:
It all comes down to a matter of identity. As for myself, I am a husband (though not a father). However, I am also: a RM, law student, avid reader, blogger, video gamer, sports fan, etc. While I am all of these things, none of them (nor the sum total of them) is ME. Sometimes, husband is the role that best defines me and is dominant. However, at other times, the role of husband is subsumed beneath other roles, though it never completely disappears. As my wife knows all too well, I jealously guard a piece of me and a time for my own independence. I reserve my own right to, and respect the desire of other married people to do so as well.
Even if it was unspoken, I believe that what offended so many sisters in the Church (and some brothers on sisters' behalf) was that Sister Beck seemed to be reducing their entire identity into a single role: mother. Many of our sisters may be like me- jealously guarding a part of themselves that is neither mother nor wife (or at least not wholly so). Though she did not say it, it could have been perceived from Sister Beck's comments that we (your family/children/the Church) don't have time for your to be anything but a mother right now. For women who are maintaining a piece of themselves apart or for whom the role of mother or wife is not the one of which they are most fond, among the other roles that they embrace, such a remark could be deeply troubling or hurtful.
Another point of her talk that has been addressed is the admonition of LDS women to be the "best" homemakers. It is nice to aspire to be the best anything, but the rhetoric in such a setting is misplaced. The emphasis ought rather to be on being "better" than our past selves, to being a better homemaker, mother, father, etc. than I was when I first have kids, got married, etc. We can be our "best" selves but trying to be "better" than non-LDS people in the homemaking category (and in a number of different fields) seems stupid and petty.