Is it illegal to insult someone?

I had been talking about the problems of reproduction and was speaking to a young man in an adidas shirt and questioning whether he or anyone should be reproducing.

This is the wording of the Act

A person is guilty of an offence if he—
(a)uses threatening [F1or abusive] words or behaviour, or disorderly behaviour, or
(b)displays any writing, sign or other visible representation which is threatening [F1or abusive],within the hearing or sight of a person likely to be caused harassment, alarm or distress thereby.