Chelsea skipper Terry was banned and fined £220,000 by an FA independent regulatory commission for racially abusing Anton Ferdinand, but is considering an appeal.
Barton, on loan at Marseille, said on Twitter: "Well I think that proves a lot. What an absolute farce. Twelve games for violent conduct and only four for that. FA should be embarrassed. £shambles.
"Had a vivid dream last night involving Terry, a roaring crowd and a firing squad. Ah, not the turnout I expected...
"I was expecting at least a public execution after a year.
"Twelve games!!! By the FA's perverse reckoning, I'd of got less of a ban for racially abusing the Man City players than tickling them as I did.
"In what circumstance can that be right?"
MP Damian Collins, a member of the culture, media and sport committee that produced a report on racism in football earlier this month, said Terry should now admit what he did was wrong.
Collins told the Press Association: "It would be good if there was some sort of recognition on John Terry's part that what he did was wrong. This is something football should learn from."
Liverpool's Luis Suarez was given an eight-match suspension for racially abusing Manchester United's Patrice Evra, and Collins said the FA should lay down what sanctions should be expected.
He added: "The FA have to establish some sort of consistency. If the longer ban is due to more incidents within the match then that's their right. I certainly think what John Terry got was the minimum.
"If there is a scale of these offences, the FA should give some sort of penalties people can expect."
Tottenham's former Chelsea manager Andre Villas-Boas insists Terry will be sorely missed by England following his international retirement.
"It's a massive, massive loss for England," said Villas-Boas.
"John Terry is a player with unbelievable talent and helped this country so much, and the same for Chelsea too.
"In the end they are his decisions, personal decisions.
"It's difficult for a player to take a position like this but on the perspective of England and qualification it leaves (England manager) Roy Hodgson in a difficult position bearing in mind the centre-backs he has at his disposal.
"I'm not putting into question the quality of the other players, but he is certainly missing one player of great, great talent."
Former England manager Graham Taylor said he hoped a line could now be drawn underneath the case.
He told Sky Sports News: "Having sat on these panels and made judgements myself I know those people will have come to their conclusion in an honest and proper manner - they will have had legal advice.
"Whether John and Chelsea accept is it up to them but I think it might be in everyone's interest to put it to bed."