I am of the belief (rightly or wrongly) that those 2 aren't comparable examples and is false equivalence, and they both have disproportionate consequences.
Someone that may be enjoying a spirited drive as we also enjoy(ed) doing at some one point, is not the same as a criminal in my eyes. Regardless, if I'm doing 50-60mph on an NSL and the other person is doing 65-70 I honestly couldn't really tell you if that person was actually speeding or not (the closing speed of 120mph ish is hard to ascertain if it's +- 10mph to me), I'm focussed on my driving and the road ahead. If I've driven past a camera van, or a horse, or some cyclists, or ANY hazard (and yes I consider a camera van a hazard) I would warn them. My view is, if it slows them down and creates less of an incident later on so much the better,.
Technically I'm not supposed to warn them of hazards or horses or anything, by why wouldn't you at least try? If my actions (which I couldn't prove either way) had a positive impact and slowed the person down and meant they went past the hazard safely, it may (although may not) slow them down for the rest of their journey.
Yesterday coming home from my dojo at 9pm, I was enjoying the wooshing and whistling of my car along some dark country roads (I live in the countryside), I wasn't going over the limit, but I was going at pace nonetheless. In a layby a couple of deer were standing around, it made me slow down considerably for the rest of that stretch of road as there may have been others that decide to dive across the road. Had someone warned me I'd have had my spider senses up and probably driven less enthusiastically. Ultimately nothing bad happened, but its easy to forget the hazards that can be present on the road, especially country roads with high hedges, so a warning of hazards is never a bad thing in my eyes.
I'm sure you'll disagree - but I'm happy in my decision to warn people for something minor like a speed camera. Whilst it may technically be potentially illegal (could be argued as obstructing the police in the execution of their duty, though this is often debated and rarely enforced for simple warnings), it's generally perceived as a very minor infraction aimed at helping someone avoid a fine for a relatively low-level offence (exceeding the speed limit slightly). The direct harm caused is minimal to non-existent in many people's and my own eyes.
Hiding a drug dealer/Aiding a shoplifter - these are significantly more serious actions. It involve assisting individuals engaged in activities with clear victims and substantial societal harm (drug dealing) or direct theft (shoplifting). Harbouring a suspected criminal or actively helping someone evade capture for theft are serious criminal offences with severe consequences.