Denying Application, to give a reason or not

[Chad Day]

When you deny an application do you give a reason?  I feel like if you do not give a reason it could be interpreted as violating the fair house act.  

For instance let's say you deny someone because you believe them to be a messy person or because they smoke pot.  If you say "I'm denying you because your car was filthy" that would offend the applicant. If you don't give a reason it may be interpreted as discriminatory.