Why is Peter Strzok still employed with FBI?

In remarks on Sunday Maria Bartiromo show, Alan Dershowitz said,

“FBI agents are allowed to be biased,” Dershowitz said. “They're allowed to support political candidates. That's part of the law. Where I draw the line is when an FBI agent says ‘we'll stop him.’
“That's not an expression of bias. That's not saying who we're going to vote for. That sends a message to the American people that the Federal Bureau of Investigation is going to interfere in an election, in an effort to try to stop the election of one candidate rather than the other. . .you're entitled to support a candidate if you're an FBI agent. But you're not allowed to try to use your office to stop somebody from being elected president of the United States.”