When a person asks you to dance, it is appropriate to say no if you have danced with this person before and he or she has been physically or verbally abusive. It is also appropriate to say no if the person is obviously drunk or threatening in some way. If you feel that a dancer is physically dangerous to the other dancers, you should report the situation immediately to a Chapter Board member.
Unless someone is truly offensive, it is not appropriate to say no because your partner may have a poor dance technique. While dancing with this person may not be one of life’s peak experiences, dance is only three minutes long and the experience will not kill you.