I keep two intact males together pretty much all the time & board a third. We've had the father of my two boys & three of his sons together without any issues. The father is known for throwing laid back temperaments, but we also don't put up with any sort of dominance behavior. Playing is fine but the minute hair goes up & posturing begins a swift and thorough punishment is given. Some dogs settle after being put in their place. By together I mean they're left in the house together, can be kenneled together & spend the majority of their time together.
I have Ridgebacks & they're not all mellow. One guy had another Ridgeback latch on to one of my boys face twice. I'd call it a fight but he would've had to bite the other dog back for that to be true. This boy has still been fine with other intact males that are not male aggressive. The other male may or may not have improved with being put in it's place - but the lack of discipline on it from its owner was obvious.
I don't think I'd have any place in our yard for a dog that would attack a puppy. Some forms of aggression are socialization while others are completely genetic. (A spooky dog is likely to throw spooky pups)
Anyhow - that's just my .02 from my experience keeping boys.
