A parenting consultant told me that time outs are terrible and cause serious damage to the parent-child relationship. is this true?

No: The important thing to remember about " time out" is that you are giving the child a " time out' from your attention, one minute per year of age. Ignoring your chid is the key here, not putting the child in a particular "place"

Timeouts: I have never heard that timeouts cause serious damage to the parent-child relationship. Timeouts should be used to give the child time to regroup and rethink how they can behave differently. Timeouts should be brief and not used as a punishment or for every transgression. For some children, timeouts are not effective, or cause more conflict. For those situations, avoid timeouts.