Joseph, your concept of mesirah is rooted in Czarist Russi. In the Pale of Settlement, no Jew could get fair treatment in the Russian court system. Conversely, the Beis Dins were effective and empowered to enforce their decisions. Consequently, Jews were forbidden to take another Jew to the governments courts.
Contrast that to what we experience in the U.S. . Civil Court, despite their inadequacies, are not antisemitic and , generally speaking, Jew can get a fair shake .
Beis dins, however, are toothless, powerless and have thier own inadequacies. Their decisions cannot be enforced. I’m sorry but if a frum neighbor is doing something wrong, I’m taking him to civil court
