Unfortunately, I don't think there is a right word in English to translate the subtext here, which is "it'd be such a waste to give it to you, that it's better to just throw it away".
I think you're thinking of 'yaru' (used for feeding pets, or people below you). I don't believe 'kuu' has an offensive air to it; rather, I always thought it was just more of a more casual use of the word. 'Kuwaseru' seems to be used for feeding people, whereas 'tabesaseru' (the form you seem to think would be used instead), is more 'allowing someone to eat'.
I could be completely wrong, but these are my impressions, and I would have translated it differently.
You might be right, my gut feelings are anything but guaranteed to be accurate. I have another report which basically agrees with you, so I'll probably revisit it, when I have a bit more time.
However, I will note that 食う is definitely noted by more than one dictionary I use to have at least potentially vulgar feeling to it, and all the unrestrained eating connotations, which basically makes it hard not to map it to the mysterious verb X that English lacks, but which I know from my native language.
Of course, that doesn't mean the same shade is present in 食わせる. But at least 食う I believe is a fairly close mapping, with the same "not nice unless you apply it to yourself, when it's slang" feeling present in Polish.
Yeah, you're crazy. "Pig out" is wrong: there's no indication that he was going to eat a whole lot of it. お前 and 食う, especially when used by a girl, do sound like they're meant to offend, but you don't need a treatise on slavic languages to translate it. I think we can render both the meaning and the nuance in standard English. Observe.