+0

I don’t know about Smith but I would tell you that Rio’s behavior at the court was outrageous. He was acting very arrogant.

Vs.

I don’t know about Smith but I will tell you that Rio’s behavior at the court was outrageous. He was acting very arrogant.

+1

There seems no particular reason to use "would". You could use "will" or "must".

"arrogant" should be "arrogantly".