It seems every club has it's share of nutters. In fairness to Liverpool, their response was both fast and praiseworthy:
We apologise unreservedly to Pep Guardiola, his players, staff and officials caught up in the incident.
The behaviour of a number of individuals was completely unacceptable and the club will cooperate fully with the authorities to identify those responsible.
The priority now is to establish the facts and offer Manchester City whatever support is necessary.