From the first page: “Hashem doesn’t want us to standout like sore thumbs, to speak and dress differently, to use different names and do different things. That wouldn’t be right. That would be acting holier than thou.”
In the blessing at the Torah for each aliyah., havdalah, this past week’s haftorah, are just a few of places where we are taught that the Jewish People are different, and should be separate from the other nations. We should stick out, since by sticking out, by being obviously Jews, we are the sign-pointer to Hashem. This is being “holier than thou” because the root of the word kadosh is related to being separate, separated from the mundane/secular – either something is holy or it is secular, and the Jewish People are commanded to be holy because Hashem is Holy.
All attempts at assimilation have failed miserably, the most obvious is the German Reform movement prior to WWII. Approximately 6 million Jew shave been lost, in the US alone, to assimilation, intermarriage – unfortunately, many Jews do not know who they are, and think that Gentile values are more important than Torah values, or G-d forefend, that Torah laws are even wrong, e.g. separating from the nations.
I refuse to attack other Jews, personally, and welcome any Jew into my home, into my shul, etc. – but we should not welcome and praise official movements that present themselves as representing alternative Jewish lifestyles and seek to undermine scrupulous Torah observance and diverge from the halacha in any of its details.
When a movement seeks to attract disaffected Jews by relaxing the halacha, they are not leading them to Torah but away from Torah.