Good to note that A4E are not saying that ATC strikes are not to be abolished, more that they should be mitigated to reduce their overall impact (from what I've read).
Of course, some time ago (within the last year, certainly), I saw a rebuttal by at least one ATC union which put ATC industrial action delays into context about flight delays from other sources. From memory it was a tiny, tiny percentage compared with airline operator delays due to staffing/"tech" issues.
Maybe, once their own house is in order, this might go down better.
(I've no doubt ATC industrial action affects passengers - but, again from info I've seen, it's to a much lesser extent than other sources.)
Industrial action should always be a last resort, nobody wants that in any industry. Sometimes it is necessary though, e.g. when Ts and Cs are so severely cut that safety is affected.
ATC is a leaner and leaner industry as time goes by - in essence the same as many other industries. But there is an increasingly fine line between what is acceptable and what is unsafe. In ATC the consequences of "unsafe" are unpalatable. As unpalatable as the thought that ATC staff could not go on strike over safety issues (IMHO).