If you want to avoid guests contacting the owner, you can hide the contact form with custom css:

1. Listing page- booking form

.col-md-6.reservation_buttons #contact_host {
display: none;
}

2. My booking section

.contact_client_reservation {
display: none;
}

3. My Reservation page

.contact_owner_reservation {
display: none;
}

4. Owner section in the Listing page

#contact_me_long {
display: none !important;
}

5. Owner page

#contact_me_long_owner {
display: none;
}