I don't know any serious speedrunners who consider most exploits to be cheating. Something as simple as bunnyhopping is an exploit, yet you'd be laughed at if you tried to run Quake without doing so.

True, there are some exploits which are truly degenerate, but they are specifically handled. Exploits in general are highly encouraged. Speedruns are listed in terms of the restrictions given: a specific difficulty, 100% vs any%, rules governing the timing, etc.