Muthama was arrested at Kangundo and is being transported to Pangani Police station.
He is accused of making inflammatory remarks in Narok at the weekend.
This comes hours after Gatundu South MP Moses Kuria was arrested over hate remarks.
In a Facebook post on September 5, Kuria said they were ready for another election but that they will hunt people who did not elect Uhuru Kenyatta.
"Kiambu has spoken. They have said Wembe ni ule ule (the razor blade is the same one). Wangige and Kiambu people are seething with anger. One million of their votes were cancelled by four people," read the post.
"But they are so ready to do it again. And even more. Manhunt is on tonight for the 200,000 people who did not vote and the 70,000 that voted for that other demon."
Raphael Tuju, who is Jubilee Party secretary general, said the remarks were unacceptable.
-The Star