Out of curiosity - how does going away during school holidays stop any of the above?
Imagine every child takes off 1 month every school year? The disruption to the class is going to be huge. It's a backward decision.
But most people aren't going to be taking their kids out for a month. We're generally talking a week or two max, and in many cases just a couple of days at the end of a school term.
As for why not do it out of term time - that has already been explained multiple times. Cost. I know when I was younger if my parents hadn't taken me out of school during term times I would not have been able to go on holidays - well I probably would have - camping in a field in Bognor rather than say camping in a field in France/Germany/Belgium/Italy...
The law states that you can't take your kids on holiday during term time. So some people decide they don't agree with the law and proceed to do whatever they like.
What next? I don't agree with 70mph speed limits, so I'll just drive at whatever speed I like and refuse to pay the fines?
It's also a new law that is heavily disliked. It's not a law that has been around for decades. What is essentially civil disobedience seems perfectly reasonable as a way to push the government into removing/replacing/modifying the law.

Yes I prefer that option 
