I completely agree the fact that the Arab nations attacked Israel in 1948 does not in itself justify the actions of Israel now. But you can't fail to see the connection between all the events from 1917 to 2015 that led to this situation. They're all part of of a series of actions that had both intended and unintended consequences, with justifications and blame on both sides at one time or other.
For instance, Israel couldn't have built the settlements if it hadn't occupied the West Bank. And it wouldn't have been able to occupy the West Bank if Jordan hadn't ignored its offer to stay out of the conflict in 1967. And there would have been no conflict in 1967 if Egypt hadn't decided to puff out its chest and start sabre-rattling. And Jordan would have had no incentive to get involved in 1967 if it had handed over the West Bank to the Palestinians in 1948 instead of annexing it. Etc, etc.
None of that excuses either settlement building, brutality towards the Palestinians or the murder of Israeli civilians.
And to answer another of your points, in 1950 China invaded Tibet and still occupies it today, bringing in its own population, trying to wipe out the culture of the country and brutally repressing the Tibetans. Yet nothing was said and our Chancellor even tours China to promote Britain while we daren't even officially speak to the representative of the Tibetan people.