(snipped for relevance)
I don't see exchanges, devs and users complaining how flawed Segwit it, nobody lost money ore saw critical errors. I only see that bullshit in the Bcash camp.
Can you provide me technical arguments/proof why Segwit is 'flawed' ore show it at the Github?
Yes. Fungibility.
What's the issue with fungibility that's so specific to segwit?
As I posted between there and here, Segwit creates three classes of Bitcoins. Each with distinctly different exposure to security vulnerabilities.
1) Those that are completely free of any Segwit taint all the way back to their constituent coinbase transactions;
2) Those that are not currently output from a Segwit transaction, but have Segwit taint between here and their constituent coinbase transactions; and
3) Those that are the output of a Segwit transaction.
Reliance on miners not to revert to 'anyonecanspend' - an incentive for which only increases over time.
That is, reliance on miners not to try a 51% attack. Does this imply the chain without segwit is invulnerable to 51% attacks?
No. But without Segwit, all miners were able to do with a 51% attack is roll back transactions. They were unable to steal funds. If miners choose to revert to considering Segwit transactions as anyonecanspend transactions, then they can claim every one of the outputs of all those anyonecanspend transactions for themselves. As over time, transactions tainted by Segwit is a monotonically increasing count, the incentive to roll back to Satoshi rules is ever-increasing. And the funny thing is that this would arguably not be stealing. After all, Segwit is said to be compatible, right? All the miners would be doing to claim these funds is to revert to the previous rule set. That's compatible.
Besides, any such attack would appear as a fork, which the non-mining nodes would be free to follow or disregard. No substantial change from the pre-segwit state of things, I would say.
A new ability for miners to fail to validate all portions of blocks.
You mean miners running pre-segwit software that have to skip SW transactions?
No. Due to the way the block hash is calculated under Segwit, one can extend a chain atop a block that one does not fully validate. A miner refusing to validate this portion of the block will have a minor benefit in that it can get back to hashing so many milliseconds sooner than one that fully validates. A miner might choose to operate in this manner, believing it unlikely that some other miner might have cheated in this area. If this lax behavior becomes predominant, we could find ourselves with a chain that includes what are invalid blocks by current rules.
Why don't we focus upon these issues first, before moving on?
Note that these are all recognized as attack vectors by pretty much all who have studied the matter. The only real debate is in the probability of these flaws actually ever being invoked.