I don't believe I've ever seen any such evidence. The only attempt I've seen about supporting that is a time series analysis that showed that the total tether issued increased at times when Bitcoin's price increased-- which is exactly what you'd expect to see happen without any funny business: 'crypto' mania fuels demand for both Bitcoin and tether.
I don't have any doubt that tether is up to all manner of funny business (e.g. printing unbacked coins and loaning them out for people to 'invest' in defi ponzis), but mostly its used to trade against varrious altcoins that are only traded on off-shore exchanges not used to trade against Bitcoin. The arguments that it plays some major role with bitcoin from what I see appear to be conjecture and logically unsound reasoning rather than clear and convincing evidence.
If you're aware of something better-- I'd love to see it.
Absent that kind of connection I wouldn't be surprised to see demand for Bitcoin _rise_ once the instability fear cleared: prior to tether being used to purchase sketch-coins at offshore exchanges Bitcoin was the exclusive option for that purpose.
