From howardedwin on r/Sixers:

Reasons why:

Calls himself an “old man” in a lot of his twitter posts
Mentions Jesus / god a ton. From his wiki: “Colangelo has spoken about his faith saying, “The first priority in life is to have that relationship with Jesus Christ. So your faith is number one. … God [has] a plan for my life.”
When all the other burner accounts went private, Eric Jr’s did not. Guessing the others were truly Bryan’s, but Eric Jr. was Jerry.
From the Ringer: “One of the few non-basketball accounts followed by Eric jr is an Arizona man named Lawrence “LB” Bain. Bain’s Twitter bio lists his location as Paradise Valley, a small town in Maricopa County, Arizona, that is five miles from the address of JDM Partners LLC, a financial company where Jerry Colangelo is a partner.” It’s much more likely that Jerry would follow this man, not Bryan…
Also from the Ringer: “Eric jr went on the attack. “I sat NEXT to you and [Dwyane Wade] at Beijing Olympics and saw you both being rude nasty to little kid fan,” the account said. “Had to eat yr pizza. … You showed no respect to this little kid, who are you to stand on high grounds? Never looked at DW the same after that.” During the 2008 Olympics, Jerry Colangelo, then the managing director of the U.S. men’s national basketball team, was in Beijing.” JERRY was there, not Bryan. It’s much more likely he was sitting next to Dwayne Wade as the managing director of the Olympic team.
All the other connections (e.g. watching his Grandson’s Chicago basketball team, defending Brian, criticizing Hinkie / Masai, etc.) all still make complete sense with Jerry instead of Brian.
Last but not least, rearrange “Eric Jr” –> “Jerri C”. Okay that one’s a stretch, but still.
Honestly I think it’s much more likely that Eric Jr. is Jerry Colangelo, trying to stick up for his son on Twitter. It’s already in evidence that he’ll go to great lengths for BC (e.g. snaking him into the organization), this wouldn’t surprise me at all.

I find it really difficult to believe that a man well into his 70s can navigate Twitter like that, let alone potentially have the ability to run multiple anonymous accounts, engage with random blogs, and Tweet GIFs all under the guise of trolling detractors. Then again…