I described the canonical front-running example in my first comment, as it gives most non-finance readers a quick overview of how HFTs work, without needing to describe regulations, strategies, NBBO, SIP, etc.

The specific strategy currently employed by HFTs is somewhat immaterial in the broader context of a discussion about front-running. For as long as a firm can legally front-run the market with any strategy, it can undermine the market and risklessly extract profits.