You’re either with us or against us is a truism for every team.  Everyone on your team must be a fully contributing member of the team.  If not, the team cannot function as well as it should and likely will not achieve its purpose. 

Here’s a quick exercise for you.  List out all the members on your team.  Then, ask yourself if each person is with your team or against your team.  Don’t spend much time as you already know the answer.  Don’t try to talk yourself out of putting a person on the “against your team” list.  Then, if your list includes anyone that you think is not a fully contributing member of your team then it is time to talk to the rest of your team or leadership to determine if the non-team member should go. 

Yes, go.  Again, you are either with us or against us.  Your team could have a counseling session with the person and give the individual a second chance.  In my experience, if you need to give a teammate a second chance, you probably shouldn’t.  If the individual has not bought into the goals of the team and other team members, he/she probably never will.  Dump the person now and find someone else who truly wants to be a member of your team. 

You and your teammate’s job is to achieve the goals of the team.  End of story.  Get the best, most committed people on your team and truly achieve your team goals!