Mark Cuban on CNBC's Squawk Box.

David Siegel may have a lot of new fans from his now famous election-season email . But apparently, Mark Cuban isn't one of them.

In a tweet today, Cuban – the billionaire Mavericks owner and entrepreneur – said that CEO's shouldn't tell workers how to vote. The tweet followed Westgate CEO David Siegel's email to his workers vowing layoffs if President Barack Obama is re-elected.