It's really unfair to mislead people into thinking that neutering/spaying will easily solve problems (e.g. aggression, marking, certain cancers-- if they actually do get solved) and not come with other risks. Whether it be testosterone, estradiol, progesterone, etc., these hormones affect and regulate not only what you see on the outside but also all those on the inside! Moreover, these hormones don't affect just the sexual organs but also other parts like the brain, bones and muscles. It should come to no surprise that other problems will surface once you take these important hormones away.
On the other hand, I know pet overpopulation is a big problem so that's why so many are advocating neutering/spaying. But I'm wondering, would there be the same level of support for human sterilization once human overpopulation becomes such a big a problem as well? It's shameful that we diminish the health of our little ones that we care so much about because of accidental pregnancies or bad people out there.
That said, I still decided to go ahead with Teddi's neutering today. (I was such a hot mess when I dropped him off this morning!

Teddi must've felt it because he was more anxious in the car than usual. But the vet says he's doing ok now!

I digress...) For us, the (potential) pros over-weighed the (potential) cons so that's why we did it but this shouldn't be the case for everyone.
Thank you, SweetViolet, for bringing up this discussion!