Happily this is false.
Vasectomy was invented in the 1920s, and over a hundred million men have had the ‘Big V’ since. Doctors have researched the side effects of vasectomy in tons of big long term studies, and they all agree that having a vasectomy has no effect on your libido or desire, or performance. No better, no worse.
Testosterone levels do slowly decline as you age, but vasectomy causes no change. It’s not like getting the dog ‘fixed’, where he loses aggression and muscle mass relative to a dog who didn’t get ‘neutered’. You are not losing anything except a tiny bit of the vas tube. Your testicles will still be there after your snip, and still will make just as much testosterone as ever.
Phew, that’s a relief.