How does one respond to those who believe that cursing, reviling, and invoking curses upon non-aggressive disbelievers alienates them from Islam, and what is the intended benefit of that?

Cursing means expulsion from the mercy of Allah the Almighty. It is permissible to curse disbelievers because Islam holds that they deserve eternity in Hellfire if they die upon their disbelief, and this does not change by prohibiting their cursing. The issue of disbelief and faith is not a matter for ijtihad (definition) (independent reasoning), but rather a fixed truth upon which Allah's argument against His creation has been established. Humans were created to worship Allah alone, and whoever opposes the messengers after the proof has been established against him deserves condemnation and punishment. Tolerance in Islam does not come at the expense of fixed truths, such as disbelievers deserving Allah's curse.