Opposition to speed-limit cameras exposes the absurdity of most speed-limit laws: it's a law so bad many (most?) people are opposed to having it strictly enforced. If that's not a bad law, then I don't know what is.
Not all laws that are heavily disliked are bad laws, and not all laws that most people like are good ones.
This leaves all manner of unsafe drivers free to proceed with making illegal and unsafe maneuvers on the road without a snowball's chance in hell of ever being prosecuted for it. In most North American jurisdictions, what do you think the ratio of speeding tickets to tickets for all other traffic offenses is? Do you think someone doing 55 km/h in a 50 km/h zone is more dangerous that the person who always plays chicken with left-turn traffic by blazing through the tail end of yellow lights at intersections? The person who stops traffic to make an illegal left turn in the same place every day? The person who doesn't turn on their lights on the freeway driving 100 km/h at night when it snows?
Especially in the UK.
To my mind, the goal of speed limits is to promote road safety by encouraging drivers to proceed at a safe speed that is suitable for road conditions. This is undermined when authorities build an expressway-style road that you'd find rated for 80+ km/h in a traffic engineering handbook and then set a much lower limit and have it enforced with radar traps. This is about collecting revenue, not promoting safety.
I visited Norway, which has photo radar, but also warns you that you're approaching it. The intention seems to be to get you to slow down rather than to stick you with a ticket. It works and I agree with photo radar when it is used this way.