Segwit can live pretty fine without the Lightning Network. Surely it is no solution but still a somewhat clever way to raise the capacity of the blockchain.
This statement doesn't make sense. I've said that the LN needs Segwit, not the other way around.
If we would have a sudden increase of transactions of 10th of times and would raise the blocksize accordingly ok, then some nodes might switch off. But the areas of blocksize increases we speak now about are far far away from centralization problems.
You can't know exactly how many nodes are going to be shut down at X block size limit. That's is the problem here. You're speculating and considering best-case scenarios.
Then... we have a centralization of development of bitcoin protocol development which seems to be a way bigger problem for the moment. The community was never so divided like it is now. And the reason is disagreement with the centralized decision of the protocol developers.
It is not a problem (yet). It has been like this for years and barely anyone complained. The only reason for which they're doing so now is due to the rejection of their ideas.
If someone would try to spam the network with 2mb blocks the same way he did the last days then the price he would have to pay would be a ALOT higher. Well, you might be right, it is still possible since those doing it showed their insanity to spend that amount of money to such stupid and useless act, but it will be way harder to do the same with even doubling the blocksize.
No, actually it is not going to be "a lot higher" if you're doubling the capacity. Besides, we're still talking about very small amounts of money that is needed to attack the network in this way.