Especially when it is in the holiday season and may be, for many, their only chance to have a decent break away from work. I guess it is fairly clear that I think people that have a work grievance should explore ways of settling that grievance that doesn't cause disruption and sometimes heartbreak to innocent bystanders. Times are hard for everyone so making them even harder, unnecessarily, shouldn't really be a tactic that is employed.
Although not particularly ideal for a lot of people it is worth pointing out that many cross channel ferries operate under capacity and can often fit in last minute bookings to at least get you across to mainland Europe. So if you are able to be flexible and are able to explore options other than flying, it would be worth having a look to see if there is a ferry with empty places that can accommodate you. You could also have a look at the Eurotunnel to see what is available. You just don't know when the next disruption is going to hit, so keep this in your back pocket as a reminder so that you can explore other options if it happens to you.
Hopefully it never will.