Rabbis, with what sect or denomination (outside your own) do you interact the most with?

I am quite curious, because there is almost as much variety within Judaism as there is inside Buddhism, Christianity and Islam. Do you feel like there was a greater impulse in the last 200 years to engage in theological polemics with other sects? Do you feel like you have to warn the people on the pews of some dangerous religious trend that originates either outside, in the secular Western world, or do you feel that there is the danger of slow drift inside the Jewish community towards a diversity of beliefs and practices that is not compatible with your conception of Judaism?