Research seems to suggest no link between front carriers and hip dysplasia. The root of this belief appears to come from the author of the Continuum Concept who appears to have decided it on a whim.
skeptoid.com/blog/2013/01/25/will-the-babybjorn-endanger-your-infants-health/
My main problem with the baby bjorn is that it's uncomfortable for the parent, particularly for women, whose body strength tends not to be in the shoulders but in the hips and thighs. Men's upper body strength is typically more developed and men don't tend (anecdotally) to have issues with carriers such as the Bjorn. Women tend to find carriers which displace the baby's weight to the hips much more comfortable, while men find both carrier styles equally comfortable, meaning it makes sense (in my opinion) to go for one which is good for both.
The other problem with it in my opinion is that it's a level removed from the parent, I think carriers which enable you to have a closer level of contact are better if what you want is the feeling of security that the baby gets from being carried. I mean, if what you want is a hands free method of baby transportation then perhaps it does the job anyway. But in my opinion the whole point of it is having them close to you.
And then lastly it's just irritation at the ubiquitousness of it and the way that people tend to think "baby carrier" and assume it means a BB or similar, even though there are a multitude of other options. This goes for Ergo as well, even though it's a "better" carrier than the BB, there are many other options out there and it's not the best, just the best known alternative.
The situation is better now, for years the choice of "slings" in brick and mortar shops was either the Bjorn or those awful bag/pouch slings which really were horribly dangerous and very uncomfortable as well. It's a shame if people think these kinds of products are the only option, because babywearing is such a versatile tool that I think everyone who wants it should have access to it. So the popularity of the BB is frustrating because people try it, thinking "This is a sling" and don't like it and decide they don't like slings, when really, they just didn't like the BB.