I guess more context would be helpful to clearly understand this. Many clients come into treatment with no experience in therapy at all or a distant history, for example, having gone to counseling as a child and then not returning to treatment until well into adulthood. So, the rules, such as they are, were those the client was socialized into, such as, "one does not show anger around others". Or, "A man does not cry", or "You shouldn't cry/get angry/show anything other than positive feelings in the company of others", etc. Giving someone permission in therapy is not the permission reflective of a power differential, per se, but rather letting a client know that the therapy session is a safe place to explore and express feelings that might otherwis have no safe/appropriate means of expression. I know I can't control a client's behaviors, but can only guide, suggest, gently reinforce and persuade.
Many lay people see situations such as that of Brian Wilson and his relationship with his therapist and may generalize that situation to all therapist/client relationships.