Rest easy, the article writer is confusing free chlorine, which is an disinfectant and antiseptic, with combined chlorine. Sucrlaose has chlorine atoms bound into it, just as common salt has chlorine atoms, and sodium atoms (a highly flammable, dangerous metal)  bound into it. Neither common salt or sucralose in any quantity likely to be used in yoghurt (or any food for that matter) has any effect on the level of bacteria in yooghurt or the gut.    As sucrlaose is 600 times sweeter than sugar the amount added to yoghurt is very, very small, and has no known effect on gut bacteria.    Another case of ill informed assumption I'm afraid...perhaps they're also a member of the flat earth society.... ;-)   Now, maybe you should worry instead about all that dangerous, inflammable metal sodium which is present in almost every food.....