With words like "invest" and "hoard", you're using language that short-circuits critical thinking. Surely, for example, you agree that not all investments are good? But "invest" has an undeniable positive connotation, so in order not to prejudge the outcome let's replace "invest" with "spend". Then, instead of the inflammatory word "hoard", let's use the word "save".

With this neutral terminology, we're now ready for some actual thought. We can recast the claim as follows: currency dilution is good because it encourages spending and discourages saving. There's no doubt about the factual claim—dilution does indeed encourage spending and discourage saving). But why is saving bad and spending good? This is an ethical judgment that depends on your particular set of values, but it is undeniable that currency dilution transfers purchasing power from savers to spenders. In particular, it's mathematically equivalent to combining a perfectly hard currency with forced confiscation (from savers) and transfer (to spenders), i.e., organized theft. Thus, from an ethical point of view, there is a strong reason not to give dilution the benefit of the doubt.

Regarding the so-called "gold standard", the historical evidence is not nearly as clear-cut as you've been led to believe. Though flawed in many ways, What Has Government Done to Our Money? by Murray Rothbard is a good place to start: http://mises.org/money.asp