If the rebuttal is "yeah but advancements improve the economy" -- The private sector can fund projects which are opportunities with an economic basis, they can take the risk and they can see if it is profitable in the market (ie beneficial)
If the rebuttal is "How will America stay competitive?" We cant seem to keep trade secrets anyways. [1]
[1] - https://www.bbc.com/news/world-asia-china-64206950
Edit: Also the 4 years at a time thing is probably a better choice too, because it makes them less twitchy politically. You get your 4 years, regardless of who's team is in office. This should be a win regardless of your affiliation.
One, endowments, this is thoroughly covered by others in past threads about funding on this site and in any number of articles elsewhere. University endowments are directed to specific purposes and largely do not cover basic science, nor can they be redirected to do at will. This is not a discretionary research fund.
Two, the private sector funds projects on time horizons that are far too short for fundamental discoveries to reach a technology readiness level that supports commercial R&D efforts, and in many cases, is unwilling to fund the commercial development too. You're frequently looking at a decade plus for fundamental R&D, with massive upfront costs and no clear commercialization path. Even if you have something that is ready for commercial development, it's still an uphill battle to get across the valley of death with patient capital.