The relevant question is whether the landing area referred to by the security guard is marked on charts.
If not, and the helo crew carried out a recce prior to landing, their actions would appear to have been entirely reasonable.
If it was, and no attempt was made to find a working frequency, then a re-brief might be in order.
In any event, it sets an unfortunate precedent to start putting obstacles in the way of those who are only trying to do a valuable job.
CD