I point out every problem I see, objective or subjective. I often label the subjective ones with an "IMO." And I try to layer my shredding with some compliments so that the harsh medicine goes down a little easier. I've rarely come across a manuscript (or even a piece in SYW) that's so awful I can't find something nice to say.
I do that for two reasons: (a) the writer is likely to be more receptive to my crits if he's not feeling totally discouraged and/or despondent; and (b) the writer is less likely to throw out the baby with the bathwater in revisions.
When it comes to crits on my own stuff, I sometimes go through a couple of stages with harsh comments (the ones that don't immediately resonate, that is -- some do resonate immediately and I can't wait to revise accordingly, and some are fairly easy to reject):
(1) denial ("but I wanted that to be a surprise in chapter 16!")
(2) depression ("crap. he's totally right. and I don't know how to fix it.")
(3) overreaction ("my first 15 chapters are a worthless disaster!") and
(4) acceptance ("wait. the novel really starts in chapter three, but there's really no reason I can't make that plot point in chapter 16 clear right up front. that's better. much better.")
Sometimes a little positive stuff and a sentence of explanation mixed into a critique helps me bypass (or at least speed through) the useless first 3 stages altogether. And I'm guessing I'm not alone. Therefore, I always make a solid effort to do that when I'm critting or beta-ing.
And Unimportant, I've seen a lot of your crits. They're very useful, and I've never seen one I thought was a heartless shredding.