The common theme of most of the above points is that the freedom of the innocent will be reduced or their suffering increased if the change is enacted, while less innocent people can continue to ignore the rules. It's oppression of the weakest.

In general, society should be very careful with the things it bans. Prohibition is a hammer best left for extreme situational outliers, not one that should be used for each and every thing someone happens to dislike.

Unfortunately, societal amnesia means we will never learn this lesson. We will continue to ban things too much, and be too oppressive, until it becomes too overwhelming and a revolution happens. Rinse and repeat.

I'm sure all of these examples (encryption, guns, abortion, crypto currencies) are considered by some people to be that extreme situational outlier, and needs to be banned yesterday.

Mine is proof-of-waste crypto currencies such as Bitcoin, or Ethereum before the PoS merge. Too much CO2 for too little gain.

(There's also the Ponzi aspect, but I don't think we need new laws to ban Ponzi schemes: if a crypto currency turns out to be a Ponzi scheme, just sue them for making a Ponzi scheme.)

A quicker way is to note that a given policy would be difficult to effectively enforce. People like to say unenforceable, which is rarely true given enough resources. But if there are two solutions to an issue, and one isn't as easy to enforce, that is a valid point. Using gun control as an example, restricting sale of ammunition instead of firearms might be difficult to enforce, because ammunition is easier to manufacture at home. Restricting sale of marijuana isn't effective because anyone can grow it in a closet, but testing at employment centers adds a lot more friction as you say, and you don't neednto monitor people's power usage or send around sniffer trucks.

It should be noted tho that the easiness of "finding a way", and the difficulty of enforcing the law, varies widely between these.

For example - and I say this as someone pro-gun - gun control would likely be the easiest to enforce since it necessarily involves physical things, and not easily obtainable ones at that, at least if you want efficient guns. E.g. black powder is not hard to make, but good luck trying to make it work in anything semi-auto without constant jamming. Sure, there's an active "gun hacker" scene where people come up with designs that can be made at home with readily available tools etc, and it's great as a counterbalance to heavy-handed attempts to regulate... but there are no from-scratch designs that are even close to just about any semi-auto rifle on the market in terms of firepower or reliability (the non-from-scratch designs involve making the regulated parts of the firearm at home, and buying everything that can go over the counter; in US, the latter is everything except for one part).

OTOH if you ban encrypted messaging, how would you enforce that? It's hard to detect on the wire if the protocol is specifically designed to withstand such scrutiny, so you'd have to go after distribution of software. You could force Apple and Google to scrub their app stores, but then people can still install directly on everything other than iOS, and they'd just download it from foreign websites. So now you need some kind of a national firewall to detect and block that etc. It's not that any of that is impossible, but it's certainly much harder, and it would affect a lot more people overall, resulting in more pushback.