Introducing words from other languages can be acceptable, especially if they don't translate well or have extra oomph in expressing something, like schadenfreude or chutzpah or schmuck.
It's the changing of perfectly good words to have meanings they weren't supposed to have that is the problem.
I don't think that words get consciously introduced into a language ... they sneak in unexpectedly, through a sort of cultural osmosis, when you're least expecting it, poof, they turn up. So it's not a question of it being acceptable, it just happens, sort of like evolution and natural selection. Think of new words or words changing meanings as a form of natural mutation. When something more adaptable and appropriate pops up, then it will more likely succeed in being used by more and more people.
That's also why words are not supposed to have any specific meaning. They have particular meanings by unspoken consensus, because a large enough group of people decide, consciously, but usually unconsciously, for a wide variety of reasons, from whimsically silly to shrewdly intelligently, to give words a particular meaning. It just happens. And finding out why and how this happens, is what keeps linguists and language academics in a job, it's so complex and seemingly logic defying.
Here's a colorful example of how meanings are attributed, change and partially change back again. You've heard of the phrase 'trip(ping) the light fantastic' ... it came into vogue (again) back in the '20's, part of Prohibition-Era slang, with the meaning 'to dance'. Billy Murray used it hilariously in a hit song of his and Aileen Stanley 's 'I'm Gonna Dance with the Guy Wot Brung Me ...' Anyway, it comes from 15-16th century English when dancing was often described as 'tripping the light fantastik toe' - making very fast and coordinated movements with the feet while standing more or less still, as was often the custom then. Tripping then meant nothing much more than dancing the hit crazes of the times. But somehow 'tripping' later evolved into meaning falling over your feet (no doubt because many dancers then did stumble over themselves). And then somehow the phrase, seemingly no longer in use, makes a reappearance a few centuries later and catches on just because it sounds so appropriate.
So what to make of this? Who's to decide what 'trip' should mean? Or what 'dance' should mean for that matter? Meanings and definitions are often just a temporary consensus and when a different or better use for them is found, another consensus will evolve.
Now, I know we're straying a bit here, but this is very intriguing, how people view language. Where I live in Belgium, language has become something of a political fetish at times, and not the fun kind of fetish either. That's why I love English and the way it just does its thing, and goes merrily on its ever evolving way without any 'by your leave' from anyone or any authority whatsoever ...