I really dislike this manner of recommendations. "Serious injury or death" with this tone implies that it will be instant catastrophe if you tow over any recommended or published limit. It's just a step below the "You'll get sued into oblivion if you tow over the limit and crash". it hyperbole that stems from a misinformation.
I'm not advocating to tow above a published limit, I'm advocating to drop the dumbass scare tactics (and don't act like it's not), and for people to do their own individual risk assessments.
Look at any number of situations and think about how any additional capacity would have helped. Emergency lane change, panic stop from someone pulling out in front of you, or perhaps a failed tow vehicle tire or component. How does the extra safety factor help or hurt. In most cases, the margin is so thin between coming out unscathed and landing in peril that you could easily attribute it to driver experience and attentiveness. Personally, I'll take an alert and competent driver in an overloaded X5, than I would an overconfident new driver in a F350.
@dimbmw your X5 is going to be at or near the limit. I probably wouldn't tow a 25ft boat with that vehicle. Doesn't mean you need to upgrade to get it home, or even to try the first few tows with it. I've towed my 3,200lb AR190 with a Traverse that had a 5,200lb limit and it was absurdly poor experience. I've also towed 7,500-ish lbs of vehicle and trailer behind my Q7 (that's rated for 7,700lbs) and felt like it had WAY more in it resulting in an excellent experience. Point being, evaluate where you're going to be towing, learn the terms of how towing works, and where you stand on those terms, then determine your comfort level with the situation.
Our advice here is worth exactly what you've paid for it, so keep that in mind too.