The problem right now with Heroes, or one of the few (there are a lot), is that the playerbase is very divided on what is/isn't a good play or build. The community is plagued with this divisive attitude due to a number of things.
General Hero Selection
"Proper" Hero Builds
Those are the three big ones I've run into. Just as an example:
Oh, you picked Nova? -> GG, she's terrible.
Oh, you took Triple Tap? -> GG, scrub Nova.
Oh, you're trying to pick off stragglers? -> WTF WHY AREN'T YOU IN LANE?
There's no real consensus in the majority of the community because the community isn't really communication in any one, localized place. The difference in opinion is astounding in many cases and often leads to situations like yours. If you want my sincere opinion, based on your story alone, then you were in the right. Defending is critical and regardless of the xp minions get you (which isn't even the concern in that situation) a few catapults on your core can be death.
Aside from that, there isn't much you can do. I know better than I would let on, but the community has had a lot of really sour people pass through and it's done substantially more harm than good. If you're looking for someone fun to play around with, I'm usually available for Heroes. ^-^