Yes.
This is why VISA was instrumental in the 'war on porn' and why every service provider ever has a provision in their contracts stating they can terminate your online presence at their discretion.
That's a way for the industry to avoid becoming government regulated, as long as this self regulation takes care of the worst excesses companies will continue to be able to operate in relative freedom.
The few times that local national law (such as in France and Germany) has butted up against companies trying to re-write the law in a more lenient way this has - predictably - failed.
But as long as companies stay on the far side of that line they are free to draw more restrictive lines as they see fit with impunity so long as those lines do not affect the lives of so called 'protected classes' in a negative way and because of the item that triggers that class to be protected in the first place.