If the well to do can boo at
the opera then it should not be surprising that MvdP gets booed at too. If you're a public figure, then the paying public can come with unwanted reactions.
In the heat of the moment, it probably seemed justified, but come tomorrow and calmer heads, then a public "mea culpa" might be the best idea. Froome got fined 200 Swiss Francs for punching a guy so a fine seems likely, and if MvdP sends some beverages to the guys he might make himself a few friends (and get less hassle in the future).