It's not groups, but groupthink they find anathema. A group of individuals coming together for a common purpose is a matter of each individual's personal choice to support another's quest for excellence, from an Objectivist standpoint. Enlightened self interest comes into play in group initiation, knowing that supporting one member's initiation will also make yours easier. It's also a matter of elevating a philosophical ideal followed by other members: the more powerful your fellows, the more protection you have from looters and mooches. Participation in Ordeals, however, would be another kettle of fish altogether. "Need help with that metaplanar quest? Sure. Yeah, I've done it before. Want to know how I did it? Sure. 5k. Want me to come along and help? Sure. I just need you to clear up a little matter for me . . ." Interestingly, it could possibly work the other way for, say, a masterpiece. I suspect they'd treat initiations within the group as recognizing an achievement amongst achievers, rather than bestowing anything or "allowing" someone to ascend up the ranks. It would probably fall into the "A = A" category, simply recognizing a member's advancement as a factual event.
Objectivists don't help people because they need help, but because they've earned it, whether in service to the cause or in work honestly given. Altruism is a dirty word, viewed as stealing from yourself and treated as harshly as stealing from another.