If your whole argument is that HFT is bad because it's "front running" or "insider trading", and you can't define the terms in ways that don't also invalidate the commonplace ways everyone accesses the market today, then what we haven't isn't a mere semantic argument; it's that you don't have a coherent argument at all.
Is HFT not front-running or insider trading? (I'd agree!) Then what's wrong with it? Otherwise: what's the useful definition of either of those terms that you're working from?