The Egypt international sparked controversy after posting that he wanted the Reds to return to being a “heavy metal attacking team” feared by opponents.
The statement arrived shortly after Liverpool’s 4-2 defeat to Aston Villa, a match in which Salah returned from a hamstring injury as a second-half substitute.
Nicol, a former Liverpool star who won multiple major honours at Anfield, stated the African would have handled frustrations privately rather than publicly questioning the direction of the team.
"He is somebody who every single Liverpool fan have looked up ever since he put a red shirt on and he's done nothing but give his heart and his soul and everything to Liverpool and Liverpool fans and Liverpool Football Club," Nicol told ESPN.
"But to do this now, right at the end of his time at Liverpool, I think it is complete and utter madness. And I don't understand. Is he angry? Is he angry at the manager? I mean come on. I don't understand why he is doing it.
"You know, everyone is looking forward to saying goodbye to Mohamed Salah. So why do you want to go and tarnish it? There will be some who will be looking at it and thinking: 'Hang on a second, why are you criticising our club?'
"We all know it's been tough season. We all know things haven't gone well. We all know Arne Slot hasn't good a great job this year. So why are you shoving it down everyone's throat? I can't tell you how disappointed I am in it, you know.
"I think the guy has been absolutely superb for Liverpool, he's been a fantastic player and up until now, for me, he has conducted himself at the highest level and then he goes and does this."