If they make waving Palestinian flags in Jewish neighbourhoods a crime (and there is a case for it being a public order offence), they should also make waving Israeli flags in neighbourhoods with large Arab or Muslim populations an equivalent crime.
As with everything it comes down to intent and context.
If you accidently throw bacon on to your neighbour's garden, it's probably a mistake.
If you purposefully throw bacon on to your neighbour's garden, it's probably littering.
If you specifically throw bacon on their garden because they are jewish/muslim/vegetarian, etc, it's probably a public order offence.
The people that run the friends of palestine stand in the centre of town handing out leaflets on a Saturday afternoon and encouraging boycotting products from illegal settlements aren't doing anything wrong.
But someone who purposefully goes to a Jewish part of a town to wave a flag for the sole purpose of antagonising those who live there, it's probably a public order offence.
In Australia, the people handing out leaflets calling for boycotts would have been committing a federal crime (at least a few years ago), as advocating boycotts of allied countries was outlawed under the expansion of sedition laws after 9/11. I’m guessing Cruella is taking notes.
I lived in a house once that only had a little 1m high fence between the front gardens / drive of my house and next door.
The bins for each house were either side of that small fence, so basically next to each other. I'm sure if a bin bag had split when I was putting it in the bin the bag's contents would have fallen on both sides of the fence.
Anyway, the point is simply that things can happen purely accidently and not break the law, which in another context - especially when done with purpose and intend - would break the law.