Yes, it is a censorship. It is manipulating the output in order to not provide an information, that would be otherwise available, caused by interest of some third party.
To expand on the topic:
1) it is not illegal to tell other people where to find bootleg software or media,
2) in many countries it is legal to download such software or media (and they pay for the privilege in the form of an extra fee on their blank media, memory cards and hard drives, whether they do it or not)
3) what is illegal is to distribute software or media without the consent of the rights owners.
Point 3) is an issue between those sites that do it and the rights owners, nothing between the end users or search engines. Neither of them do 3) themselves.
Nobody of us might like spam, but there is obviously something that keeps these in the business. What? Eradicate that, remove their cash flow.
I might not like sites that aren't mobile friendly, but fortunately, when I'm not in a mood so scroll around it, I can always close it. No need for Google to step in.
I also do not like children being presented with porn/cigarette/alcohol/whatever advertising/results. But - these result do not come themselves, they are initiated, usually by those children. There is more need for parenting, than for Google protection. If it really bothers you, most routers allow for filtering the web, and some ISPs provide that as a service - for those interested, as it should be.
The problem with common sense vs censorship is: where you draw the line? That's the hard question, and easily abused one at that. Especially by entities like Google, who are not a harmless protector of innocent or knight in shiny armor. They are businesses, who have interest that may not align with yours, especially in the long run.
There are a myriad of search engines out there. They have competition.
I would say Google's right to do what google wants to do trumps any real arguments against them doing this here. I doubt they'll have any notable downtick in users.
Of course, you right to have an opinion on their practices is valid, i hope its not coming across as if its not, i just wanted to focus on the realities of the situation for the broader reading audience
And arguments for it are similar to the usual "think of the children" way of thinking which eventually leads to harder censorship, more surveillance and generally poor place to live.
Side note, I'd like to hear the age of people who argue either side of this topic.