Can an employer force a sick employee to go home?

Yes. Employers control their workplace and set the terms and conditions of employment. If someone is sick and the employer is worried they may get others sick or otherwise impede workplace productivity, they can absolutely send them home. Look at it this way: an employer may, in the absence of a contract to the contrary, fire an employee at any time, for any reason. They may therefore take steps short of that, such as sending a sick employee home.

Yes, an employer can do this.  And would argue that they probably should.  The reason - most employment relationships are what is known as "at will".  This means that basically the employer can hire or fire someone for any reason or no reason whatsoever, as well has increase/decrease salary/hours, promote/demote, and generally impose requirements as they see fit.  In turn, you can work for an employer, or not, your choice. 

Exceptions to the above would be if there is a stated company policy covering this, or there is a union/employment agreement that governs, or this situation has arisen due to some type of discrimination.