In the 17th century the Dutch were more tolerant than other European countries. This was a result of of how the country was formed and how society was organised.

The Dutch Republic became independent at the end of the 16th century. Philip II, king of Spain and lord of the Netherlands, had introduced several impopular measures such as increased taxes, less power for the cities and the nobility, and - crucially - a ban on non-catholic religious beliefs. The relative importance of these factors may be debated, but all played a significant role in sparking the Dutch Revolt which resulted in the Dutch Republic.

In the Netherlands, protestantism was wide-spread. Especially in the western provinces, a significant portion of the population - including nobility and wealthy merchants - had protestant beliefs. Other provinces remained mostly catholic. Philip II's persecution of protestants led to civil unrest which swept the provinces. In response, Philip sent an army from Spain to put an end to the unrest and to root out protestantism.

As it happened, the unrest had mostly died down by the time the army arrived, but the arrival sparked new unrest and even open revolt by some cities (mostly in the west) and nobles. This revolt was led by William of Orange. It cost a lot of money to maintain the army in the Netherlands and after about a decade Philip was unable to keep up with payments. The result was a mutiny of the Spanish soldiers, who started sacking local towns and cities - even in the catholic provinces.

The mutiny led to a treaty by all 17 provinces in the Netherlands declaring that they wanted the Spanish army to leave and the old political situation restored. Moreover, they declared that they, not the king, would determine how religion would be organised in the Netherlands. This was a sticky and divisive issue though, so they didn't do anything more than declaring that they would determine it at some point in the future. Three years the provinces split over this issue. The southern provinces decided to only allow Catholicism and to stay loyal to the king, the western provinces decided to form a "closer union" (effectively a new country) and allow freedom of religion.

This explains the religious tolerance of the Dutch Republic. Note though that 'freedom of religion' only meant that the state couldn't force people to adhere to a certain religion. It did not mean that all religions could worship openly. For instance, some provinces and cities banned catholic churches (the buildings, not institutions); in those places Catholics had to congregate in attics which were repurposed (and redecorated) for their worship services.

There was more than religious tolerance though. In other European states kings and princes had control over the press and universities. It was difficult to publish ideas which ran counter to the ideas of the king. In the Netherlands, there was no king to stifle the exchange of ideas. Many European scientists and philosophers went to the Dutch Republic for this reason. To name just a few: René Descartes wrote his important works while living in the Netherlands; John Locke lived in the Netherlands for several years after things got to rough for him in England; Voltaire published a book which was banned in France via a Dutch publisher.

To answer your question, the Dutch were actually "truly tolerant", at least compared to other European nations. Of course this also helped their business. Whereas other empires had a strong religious component, attempting to convert the local populations, the Dutch were content with trading and running plantations (with the associated subjugation, slavery and other atrocities - but not forced conversion of entire populations). For example, one of the reasons the Dutch were the only ones allowed to trade with Japan was that they didn't proselytize.

Why would you think that Dutch were 'tolerant' ?

For example, South Africa was originally colonised by the Dutch and it became one of the most intolerant (institutional racism) countries until 1994, when finally all citizens of South Africa were allowed to vote.

In Indonesia, the Dutch were not at all 'tolerant' but followed the typical colonial policy of profits before people. It took the Indonesian people four years to get rid of the Dutch (1945-1949), who didn't want to take the hint and leave. This is one of the darker episodes in Dutch history.

Lastly, Suriname may be a multi-cultural country, but during the Dutch colonial days, the was a system of de-facto apartheid which favoured the Dutch Colonial System. Independence was achieved in 1975, but it has not been easy for the ex-Dutch colony, due to the corrupt system 'tolerated' by the Dutch Colonial System.

Thus, there is no such thing as a 'tolerant' colonial system. Making colonies by its nature, is very intolerant.

Recommended reading would be, 'Zwartboek van Nederland Overzee' (E. Vanvugt) which shows just how intolerant Dutch Colonialism was.