The ancient Roman Colosseum will be the venue of gladiator fights — albeit staged — for the first time in two millennia under a $1.5 million sponsorship deal with Airbnb that aims to promote “a more conscious tourism.”But some visitors to the monument Thursday, as well as housing activists, were skeptical about the value of the arrangement, citing ongoing controversies in many cities over the role of short-term rental platforms in fueling overtourism and limiting affordable housing for residents and students.Under the deal announced by Airbnb and the Colosseum on Wednesday, the sponsorship by the short-term rental giant will cover the renewal of an educational program inside the ancient Roman amphitheater covering the history of the structure and gladiators.Eight of the platform’s users and their plus-ones will be able to participate in faux gladiator fights after the Colosseum’s closing time on May 7-8, taking the same underground route used by …