Sorry. If you are prosecutor, extreme bias requires you to recuse or else the whole investigation is tainted. Same for a judge. Even Mueller saw that and got rid of Strzok as soon as he could although Strzoks fingerprints and actions were all over the Hillary and Trump investigations by then so you can't undo the damage just by having Mueller dump him.
In addition the difference in treatment between the two investigations that Strzok worked on- Hillary's and Trump's- provides overwhelming evidence that the aforementioned bias influenced the goals and actions of the investigations. That is beyond dispute at this point.
Also you are stuck on stupid with that old argument about how this is just a matter of every public employee having the right to a political opinion. That worked for a about a week but the subsequent waves of emails and texts released showed a bias and a venom and a willingness to use public authority to accomplish a political goal. "Insurance policies" to be put in place, "meetings in Andy's office to discuss options about Trump," Texting each other and saying "we will stop it." Saying things like "I was in Walmart and could smell the Trump supporters", and "Trump is a loathsome human being."
How would you like to be a black person being investigated by a prosecutor who had already decided that you needed to be stopped and that he can smell your people in Walmart? and was clearly giving you a full throttle investigation when all his white buddies got the hillary version? No. There is the right or public employees to hold political opinions, and then there is a venomous predisposition that negates the legitimacy of the process.
And no, McCabe's argument that he did not need to disclose the 750,000 that his wife got from dem organizations because that is included under his right to have political views on his own time did not fly either. Not sure that -since you are still stuck on stupid on the other issues- that you are still stuck on that too. Most likely you are. Things have advanced a bit since then. You remember McCabe and Lisa Page right? Gone.