To understand the point of view of this cartoon, look at who it is by and think about what they would think of English imperialism.
This cartoon is labelled as a German cartoon. This means that it was drawn by someone from a country that was a rival of England's in the Scramble for Africa and other imperial ventures. The Germans would want to try to make the English look bad so that they could claim to be morally better than the English.
The cartoon implies that the British squeeze their colonies hard all for the sake of money (the coins). They pretend to be righteous (the preacher) but they are really just in it for money.
With this cartoon, the cartoonist is emphasizing how the British exploited natives in order to gain more wealth. It is basically a very vivid representation of how natives of colonized Africa were exploited and used. It is well known that colonial powers in Africa stripped the continent thoroughly of its natural resources and did little for the natives in return.
I also agree that the cartoonist feels that the British had a morally superior air about them while exploiting their colonies. They are giving the African something to drink and praying for his soul as they torture him to gain wealth. The point the cartoonist is trying to make is about the hypocrisy of the British. It appears that the British believe that they are doing something good but they are actually just exploiting and harming those people for money and resources.