One of the main differences in approach between religious and non-religious Jews is how they define a "good" Jew. For religious Jews it's based mostly on personal practice and the regular learning of Torah. For the non-religious definitions are based more on an ethnic basis. Just like someone can be a good Italian simply by accident of birth and a like of ravioli, one can be a good Jew if one has even just a Jewish father and a liking of blintzes on Sundays.
Neither approach is entirely satisfactory. While the Torah approach has more legitimacy since religious practice and learning has been what has kept our nation strong and distinct from the surrounding cultures for the last 3000 years it is foolish to assume that it can be the sole defining feature for what makes a Jew. It fails to account for not only those legal differences in practice between Sephardim and Ashkenazim, for example, but also the cultural things that give each group its special flare.
Why does this matter? Shouldn't Torah be enough? Shouldn't we simply define our comradeship based on mutual appreciation of learning and practice?
I would venutre to say that it is not enough for a couple of reasons. As keeps getting demonstrated almost daily it is quite obvious to state that Torah learning and personal practice does not a mensch make. In fact reading the news out of Israel you sometimes sadly get the opposite impression, chalilah. Based on my personal feelings it is sometimes very difficult for me to walk down the street in Bene Beraq and feel like I have anything in common with some of the folks on the street there. This is not a good situation.
Another reason concerns the greater good of the Jewish nation. Although, nebich, most Jews are not properly Torah observant (if at all) that does not make their innate status of Jews less valuable. They have their place in God's grand scheme of things even if their personal level of practice suggests they don't agree. We have enough enemies willing to reduce the size of our population. We need not assist them through disenfranching our co-religionists.
What's more, despite their lack of observance there is much we Orthodox Jews can learn from them. ON one hand an ethnically exclusive approach to one's Jewishness leads to Howard Wolowitz - a stereotype that amuses the gentiles who watch while causing those who know what real Judaism is to cringe. On the other hand might someone like Howard, befriended by frum Jews, have turned out more involved religiously, more conscious of his Judaism and its obligations?
There is also a general sense of nationhood to consider. If I meet another Jew I am not just meeting someone who puts matzoh balls in his chicken soup for taste. I am meeting someone whose history goes back 3500 to yetzias Mitzraiym and beyond. It doesn't matter if he's from Israel, Russia, South Africa or China. When I see a Jew on the news he's one of mine. This sense of camraderie is one of the factors in our survival after all the hardships we've been through. And that sense doesn't necessary come from personal practice and Torah study. How many ultra-Orthodox Jews are quite dismissive of Ethiopians because they're the wrong colour or demand that Sephardim wear Orea cookie outfits if they want to be considered properly observant?
Look at Israel right now, the conflict between the seculars and the Chilonim in particular. With the language flying back and forth you'd think mortal enemies were about to clash. We are talking about Jews against Jews. Shouldn't there be some moderation, some reaching out because we are all the same nation?
We are right now during the Three Weeks and Tisha B'Av should be a stark reminder that sinas chinam put us into golus and is keeping us there. No, we can't approve of the ethnic Jew's claim that he is being "good". We have standards that demand practical observance and learning of us. But we must continue to feel a sense of brotherhood towards him or we are lost as a people.