I dont get your logic. My logic says that printing tether should boost Bitcoin price. They buy bitcoin or other alts with this tether. A lot of tether was printed at end of 2017 when price of Bitcoin was hyperbolic.
What is the main reason behind printing tether because why don't we trade with the current supply of tether? Whether tether printing will make us increase the price of Bitcoin and it will affect the price of other altcoins.