The former Wizards star took aim at the Association in a passionate conversation with TMZ Sports earlier this week ... explaining he believes Ja's suspension for wielding yet another firearm on video should have been significantly less than what it ultimately ended up being.

"It's too harsh," Arenas said bluntly.

As for why ... he said he thinks it was all based on subjectivity -- not precedence.

Arenas told us ... most guys that he's seen get popped by the league in the past for gun-related offenses have only received 1 to 7-game bans -- making Morant's lengthy suspension super unfair.

"It's public perception," Arenas said. "The public wants him to be stopped. So, now the NBA comes in and says, 'All right, we have to make it look reasonable.'"

Arenas said Morant already suffered greatly off the court -- something he believes Silver should've factored into his punishment.

"He's already taken Ls," Arenas said, noting the small breaks that Nike and Powerade took from Morant. "He's taken Ls on his public image."

Arenas told us he thinks it's all so unfair, he expects Ja to appeal ... and win.

Of course, Gilbert has plenty of experience in this field -- you'll recall, he ultimately lost 50 games of his career following his infamous 2009 gun incident.

He said he's actually down to help Ja learn everything that he gained from that big ban ... telling us if Morant reached out, he'd definitely answer.

For the Memphis star's part, he apologized for his actions that led to Silver's decision ... saying to his fans, "I hope you'll give me the chance to prove to you over time I'm a better man than what I've been showing you."

We also talked to the former NBA star about the incoming rookies. Arenas offers advice to the young hoopers ... and gives his scouting report on Victor Wembanyama.