Sure....IPMS has a long history and some of it involves alienating model builders. Some of the criticism has been rightly earned, at least in THEIR eyes. Like the saying goes...."haters gonna hate"....
I've been a member for over 40yrs now. I've seen a number of "scandals" within IPMS. I've seen a good number of the membership who are TOO serious about this hobby. This can be a real problem when they demand that everyone else in their club be as serious as themselves, while many of the members simply want it to be a relaxing hobby. We have a reputation of being "rivet counters" and "color nazis" who live to beat others down in a contest. While that's on the harsh side, there's a kernel of truth in it that's hard to live down.
The funny thing is, as you mentioned, MOST of those who espouse those views are not IPMS members, know little to nothing about IPMS, and have NEVER been IPMS members. They simply repeat the grousing they've heard third hand from people who supposedly heard it from someone who's brother-in-law didn't like IPMS.
If you actually pin down an "x-member" who didn't like IPMS and left us you'll usually find a much more concrete reason that they left. Most often, it's that they felt out of place because most people didn't build what THEY built, so they didn't "fit in". A correlation to that is the "they didn't appreciate what I built", meaning they either failed to get the praise they hoped for, or they couldn't understand why a group of people with their OWN interests aren't interested in what they themselves were interested in. Occasionally it'll be because "a club was offensive" and criticized their modeling....which usually means ONE person in that club (and every club seems to have one...) was less than tactful when asked what he thought about someone's labor of love.
As you alluded to, there's a laundry list of reasons to hate IPMS. However, most of them are somewhat out dated, and the majority of them are people expressing sour grapes about IPMS not being what they expected or hoped it would be for them.
What they always fail to mention about IPMS is that it's just about the only modeling club that tries to welcome EVERYONE, no matter what they like to build. Sure, most of us are military builders and the majority of us build aircraft and armor. But, unlike the figure clubs, auto clubs and AMPS, we welcome those who build what we DO NOT build ourselves. The Journal, although totally dependent on voluntary contributions, bends over backwards to SERVE those "others" with articles (and rightly so). Every successful IPMS club that I'm aware of makes a point to make everyone feel welcome, while also being sure that they understand the dynamics of the club they're joining so that there's no illusions.
In closing, all I can say is that modelers are a weird clique. We're generally loners who don't need a club or interaction to enjoy our hobby. There's very few (of the millions who actually buy and build models) who venture out and try to associate with others. Of those, too many will find that their attempts to combine "clubbing" with model building doesn't make it more fun. Those that DO like it will probably be okay with IPMS. Those who don't will be very likely to end up hating us....