So can dental fillings, breast implants, and artificial sweeteners.
Like female birth control though, most people agree that the risk for developing cancer associated with the activity is well worth the benefits. Saying "boo fucking hoo" about someone who can never reproduce again is pretty cold-hearted, in my opinion.
I did a quick Google and it appeared to me that most of the adverse events were measured at rates in the 10's per 10,000 ... Though that is absolutely from a very high level.
This study was presenting at around 20% (IIRC, I was reading the outrage version of this stuff a few days ago)
It is also important to note that this is by no means the end of the drug. The people involved consider this to be a very promising study and are going to continue working on it.
It wasn't stopped early "as a failure" to be shelved and never looked at again. It was stopped early because they knew enough about the upside and didn't have to continue on the down.
The next rounds of trials will likely try to alleviate the side effects while preserving the MOA (mechanism of action)
If you really want solid male birth control with no side effects, bank your gametes for $50/mo and get your vas deferens snipped.
Female birth control may not cause permanent lack of fertility, but it can cause cancer. Breast cancer. Cervical cancer. Liver cancer.