A practicing member of the con-servative offshoot of Judaism is a mumar lehachis and a koifer beikar in most cases (most of their clergy certainly are.) In addition, their definition of shomer mitzvos has little to do with proper halocho.
Having grown up in that withered branch’s institutions, I would sooner accept the shechita of a j4j or one of the five or ten mental institution candidates who proclaim that the Lubavitcher Rebbe ZYA is even more than Moshiach over that of a con-servative shochet (none of whom exist anyway). My high school principal was a practitioner of the con-servative faith and he had an indoctrination class for us in senior year in which he taught us kefira mamash as a supposed guard against assimilation and inter-dating in college. Yeah, right. Had I listened to him I DAVKA would have intermarried because he basically taught us the “man-made but divinely inspired” and “tikkun golem” bubbamaises.
The debatable “fact” that some people who davened in those institutions supposedly showed some chessed to frum immigrants (probably true as they did not know the beliefs of anyone they were sponsoring and they sponsored as many socialists and communists as they did frum people, never mind that in those days you just went to whatever shul was closest or in style regardless of its affiliaiton and few of those people knew what the movements even stood for) does not change the nature of these movements. Far more frum activists, like the leaders and volunteers for chessed organizations in EY and Chabad shluchim, stick their necks out and give all they have for largely unappreciative, often literally parasitic and contemptuous, frei Jews (most of whom, especially outside of EY, know no better but also won’t pass up a freebie when they need one) than the other way around.
What is known is that once the refugees arrived, those institutions and movements put a lot of pressure on the frum ones to assimilate. BH most held steady and ended up rekindling the flame of Torah in the United States.