The issue with David Cameron's idea is that it is a default-on ISP level filter. That it is being advertised as a filter for pornography is just a political tool, a filter is a filter. Any filter is going to be imperfect, going to slow down internet traffic to check all of it against the filter, and can have its rules changed fairly easily without oversight.
Also, because it is default-on and ISP level, anyone who wants to have proper freedom of information needs to tell the ISP. Which wouldn't be so bad if the filter was advertised as being about pornography. Because of that, anyone who demands freedom in acquiring information has to be made to feel like a pervert, and possibly publicly humiliated as such later on (because ISPs would need to keep a list).
Anyway, thanks to Google's ad policy and safesearch, it's easy to avoid porn while just browsing normally. These politicians seem to be living in 2000, when random porn popups would just happen randomly.
As for Russia, what planet are they on. Everyone bloody swears in real life.