"I’m just trying to understand how more money in circulation is bad, but government stimulus spending is good."
It isn't that "more money in circulation is bad", but that, under current conditions, it won't do much. Short term interest rates are zero, and demand for money is low, so putting more money out there isn't going to help. The thought of the Fed is that buy tossing more money in they will lower long term rates, or maybe spark expectations of increased inflation, either of which (particularly the latter), would be good, though there really isn't much historical basis for the former -- didn't work in the depression or in Japan, but is worth trying I guess.
Stimulus is good because of the collapse in private demand. Again, interest rates are zero, demand is too low for business to expand, nobody sees demand expanding any time soon and so only government can provide demand that will bring employment down (btw, this is a very rare situation which we haven't seen here since the 1930s. Contrary to some beliefs, money was tossed in by the fed, but didn't do much; possibly a lot more should have been tossed in, but it was WWII that cured the depression, in essence a huge stimulus). Again, we needed a program of about $1.4 trillion; we got maybe $600 billion, most of which was cancelled out because of budget cuts in the states. In the current climate, it's hard to see anything pulling us out for a long while. Balancing the budget, or cutting spending signficantly NOW would be really, really bad. unemployment would go way up, tax receipts would fall even more than they have, and the deficit wouldn't get much smaller, if it got smaller at all. We might even end up in a worse debt position than we are now. (that's one part of what's called "the paradox of thrift" which is generally talked about in connection with private action).