We don't have a Philistine account of the duel, or anything like it. The Hebrew account has doubtless gone through many hands and several iterations to the point where dating and authorship are largely unanswerable questions. Goliath's collection of equipment is a baffling array that seems to trace the lineage of the story through history.

The story ostensibly takes place around the year 1000, but Goliath seems to be an amalgam of a Greek Hoplite and a Homeric hero. Culturally, this seems reasonable: Philistines and Myceneans came from a similar geographic area (the Aegean) and had many cultural similarities.

The Homeric attitude toward long-range weapons is complicated. On the one hand, Homer celebrates the archery of Odysseus, Philoctetes, and Paris. Furthermore, even the basic spear of the Homeric warrior is often thrown at great distances. On the other hand, there is a reliable sense of archers being inferior, cowardly, or deceitful. Odysseus does not use his bow in wartime, only to clear his home of interlopers. Philoctetes is marooned by his comrades and only rescued out of total desperation. Paris is persistently characterized as a foppish and effeminate prince concerned more with sex and fine clothes than manly honor.

By the classical era, such attitudes had hardened significantly among Greek writers, who generally considered ranged attacks to be the purview of devious, cowardly, effeminate foreigners.

Of course, in the story we have, both Goliath and David appear to assume that Goliath's array of weapons are superior to David's. Goliath is insulted by David's sling, but does not appear to quarrel with its fairness.

And part of this is simply that, despite enthusiastic calculations to the contrary, the stones David could throw had a fairly limited stopping power that Goliath's shield and armor were more than able to protect against. Paris does not bring his bow to the duel with Menelaus, but if he did, he would have been at a considerable disadvantage against an experienced warrior with a large bronze shield.

Now all of this is not to say that a Philistine reader of this story might not have considered the sling a "cheap shot." They probably would have considered it underhanded and effeminate. But this story is not told from their point of view. It is told from the point of view of the Hebrews, whom the narrative tells us lacked bronze armor and weapons so severely that only the king and his son were in possession of them (hence David being given Saul's armor for the fight).

Think of the dynamic as similar to contemporary contests between wealthy imperial powers and native peoples resisting through a combination of determination and guile. The Hebrews do "fight dirty" as far as the Philistines are concerned, but they lack the equipment to "fight clean" even if they wanted to. They are despised more for being savages as for being cheats.