Why is the Federal Reserve raising interest rates to curb demand, which will then control inflation, when the high cost of gas and goods/services is already curbing spending?

Cost of gas and goods and services is a result of inflation, and not the cause. Inflation with years of low interest rates have already happened. The effective money supply has already grown. What the fed is trying to do now
is make sure that this excess money supply does not cause MASSIVE inflation.
Inflation running at reasonable numbers with them being a bit higher than the Treasury bond rate is a good thing. It means that the 8 trillion dollar debt will shrink, and that the holders of that debt are in effect losing a percent or two.