This is completely false and I can't understand how you could have acquired this impression.

What do you mean by 'obfuscating'?

A 50+% entity cannot cause permanent damage to the blockchain; they cannot steal coins; they cannot generate coins that weren't supposed to exist; the ONLY extra powers they have are

(1) to suppress transactions that would otherwise have occurred, and (2) to prevent other miners from mining.

Neither of these transactions has any permanent effect on the blockchain after the attack stops, except for the omission of transactions that would otherwise have been present (which, assuming they were organic transactions by real users, will be automatically resubmitted until they're included in a subsequent block.)