In Johnson's case, there's a bit more to it. He talks about not negotiating with the RMT "as long as it holds a gun to Londoners' heads", but has not met with the union for nigh-on five years. This is part distaste for the hoi polloi, and part calculation so he can trot out this transparent line when occasion demands. The second thing is that Bob Crow condenses in one man absolutely everything Tories like Johnson hate about working class trade unionists. He's militant, refuses to "know his place", is successful and worst of all, refuses to be taken in by the Boris Johnson Show. If Johnson can take him and the RMT out, he can lay credible claim to Thatcher's union-busting legacy, deepen his base in the party and extend his appeal among those backward types who see the pay and conditions of Underground workers as something to vilify, not to attempt to win for themselves.
Like the rest, Johnson is fully immersed in the stunted outlook and smug decadence gripping his party. Therefore, I'm not in the least bit surprised he (and Dave) haven't properly thought through the unintended consequences of their move to impose ballot thresholds.
The first is well-trailed. As the New Statesman points out, Johnson wouldn't have been elected if the threshold was applied to mayoral elections. The same can be said for European and local authority elections, parliamentary by-elections and, in some cases, a few constituencies on general election day. Johnson himself was elected on a 38% turnout. The RMT's ballot managed 40% which, as it happens, is quite high for an industrial dispute. The mayor has been asked about this comparison frequently, and a typical routine of muttering and mumbling comes by way of reply. Some might say a strike ballot and election are two different things, but Johnson knows the legitimacy principle is the same for both. And so do the public. He is canny enough to be aware that every time he gibbers something about the threshold, he is dumping over his own standing as an elected politician. Yet, simultaneously, he ignores the signals his antennae are picking up as if it won't affect him. He doesn't care that prodding a socket with copper wiring would give politics a nasty shock. The oaf is ultimately undermining his and his party's medium and long-range interests all for narrow egotism and a deluded sense of invulnerability. Decadent is one word for it. Another, much shorter d-word also comes to mind.
The second is less considered, but could be of equal - if not more - significance. Johnson and Dave favour the threshold because a) it will be more difficult to pull off official disputes, b) demoralise union activists as thresholds are repeatedly missed, and c) cost unions more time and resource to meet the new criteria. Quite apart from restrictive new rules running the risk of midwifing wildcat strikes or, more likely, individual acts of workplace damage born of frustration, it's yet another example of complacent suppositions. Remember, the relationship we as labour movement people have with unions is atypical. We go to meetings for one, and we earnestly talk about union issues with real-life people in real-life places. For most trade union members, the relationship they have is the missive through the door and the monthly deduction of subs. A good chunk of workers in organised workplaces won't even know who their local rep is. Consider what might happen if the law changes. A dispute arises, a union goes for a ballot and has to hit the thresholds. It has diverted more resources into a get out the vote operation. That could mean more workplace meetings, more literature through the post, more activists working on turnout and, who knows, a canvassing of members' homes. This is easier to do on a smaller scale, so it's likely disputes involving hundreds or thousands, not tens or hundreds of thousands would become the 'standard' official dispute. But more importantly, the turnout pressure could force members into a closer relationship with their union. A distant, abstract entity might become something more approximate, more immediately relevant, more direct. That's the last thing Johnson and Dave would want.
These things won't necessarily happen, but they could. The question is are Tories willing to run the risk? Given their sectional stupidity and dislocation from the collective interests of British capital itself, there's no evidence they think there even is one.