This is a common accusation made by ignorant Islamophobes, who are often just parroting low-lifes who have no credibility themselves. But when this accusation is scrutinized, it inevitably falls apart. First, there is literally no evidence that the Prophet “robbed” the Quraysh caravans. In most of the encounters, the two parties avoided fighting. In one instance, a man from the Quraysh was killed and the Prophet actually paid compensation to his father! Would a “robber” do that?
But there is another reason why the “robber” accusation doesn’t work. When the Prophet was leaving Makkah for Yathrib (later renamed Madinah), he had possession of people’s goods that they had trusted him to hold for them, sort of like how a bank has safe-deposit boxes. Had the Prophet wanted, wouldn’t he have stolen those goods and take them to Yathrib? Instead, he arranged for Ali Ibn Abu Talib to return those goods to their rightful owners. This shows the sincerity, honesty, and integrity of the Prophet Muhammad (ﷺ). See below.
Oh you haters, come to your senses. You have been fooled into hating Islam and Muhammad (ﷺ) by the devils you look up to. But they will lead you to only one place: hell. Use your reason. Don’t blindly accept what the liars tell you.
Additional information: https://youtu.be/8IxHYq6uXS4