Unifying with Food

Rabbi Sion (Zion) Levy a"h, was the Chief Rabbi of Panama for 57 years, during which time he encouraged thousands of people to increase their level of religious observance. 

I read that the first thing he worked on was kashrus, probably for both spiritual and practical reasons.  What caught my attention in an article about him is that it said he promoted kashrus as a way of unifying the community, because if everyone adopted kashrus, at least in the home, the whole community would feel comfortable eating in each other's homes.

We have halachos that are designed for the express purpose of keeping us from socializing with non-Jews such as bishul Yisrael, pas Yisrael, yayin nesech, while our kosher laws unify us.

So what happens ... frum Jews undertake standards of kashrus that differ from one another! This goes so far that even among frum parents and children, and among frum siblings, there are different standards, such of which are mutually exclusive (for example, if one will only eat a certain shechita and another will only eat another shechita). 

There have been individuals who took it upon themselves to eat nothing outside their own homes, out of kashrus concerns. 

I think this is quite sad.  Even more than sad.  It seems wrong that our piety puts barriers up between us.  Many decades ago, it may have been necessary to have a safeguard like that (not to eat anywhere but at home), but today? It treats fellow Jews like non-Jews and that is troubling to me.

What is the solution though, for those who have kashrus standards that others don't have? I suppose it's a question for a rav.  My approach is to eat at the homes and simchas of relatives and friends if they are known to be reliably kosher people.  If they serve items (it's usually the vegetables that need checking that are my concern) that I'm not sure about, I will either not eat them or might ask what they are using.  I don't like asking because I am uncomfortable quizzing frum people about their kashrus; it seems insulting.  Other solutions are welcome.