I have. Heck, I used to be one myself.
If you believe that homosexual behavior is against God's order, you are labeled an intolerant fundamentalist bigot.
That may be. Neo-evangelicals would say that homosexuality is sin, but would emphasize that we should be accepting of homosexuals without condoning their behavior, rather than railing against the Sodomites, as the Fundamentalists do.
It is the post modern neo-secularist lefties that have caused the division. Not the conservative fundamentalists. All they want to do is to hold fast to their profession of faith without wavering.
Look at the Presbyterian splits of the 1930's. Those are considered the key case study in the Fundamentalist-modernist contraversy. The Fundamentalists, when they split the PCUSA, first of all abandoned the denomination to slide deeper and deeper into ruin, and while Westminster Theological Seminary is a good seminary, Princeton was abandoned to the liberals. Fundamentalists backed themselves further and further into an academic ghetto, and only recently have schools like Baylor and Wheaton been able to extricate themselves.
And then there was the Presbyterian split. The Orthodox Presbyterian Church, which split from the PCUSA, itself fragmented to create a second Presbyterian denomination, the Bible Presbyterian Church. This split - over relatively minor issues like premillenialism and prohibition - was so acrimonious that it actually shook Francis Schaeffer's faith and turned him atheist for a brief time period.
Now, I tell this tale of woe, not to dump on the Presbyterians - I am a Bible Presbyterian myself - but to explain where fundamentalism failed - and it's true across denominational boundaries.
The single biggest point of failure for fundamentalists is the inability or unwillingness to impose negative sanctions against institutional covenant breakers.
Or as I like to say, "What we have here....is a failure to excommunicate."
I believe you're pointing out that the desire to split theological hairs -- to "be right" about relatively minor issues -- can lead to hyper-sectarianism. I agree, but I suspect that many people have heard "fundamentalist" used so often by the enemies of orthodox Christianity that the word makes them highly defensive.
In a fallen world, there is a tension in any church between two poles -- between the rigidity that can fracture a body into sects with little or no real difference between them, and the "inclusive" tendency that will open the door to the kind of heresy seen in the mainline denominations.
An example of the first tendency is the continuing Anglican groups in North America, which are split into at least a dozen rival bodies, and therefore appear unable to offer an effective alterntive to ECUSA. The various conservative Presbyterian churches can also illustrate this (I belong to a conservative Presbyterian "splinter group", so I mean no offense here.)
The obvious examples of the second, "big tent" tendency are the ECUSA and PCUSA themselves.
You can probably predict that I think it is a lesser evil to lean toward the doctrinally rigid end of the spectrum. The reason orthodox churches end up dividing over issues of theology is because they care about theology in the first place, which is a good thing. The sectarian divisions between conservative Presbyterians are a waste of human and financial resources, but at least a "seeker" walking into one of their churches will hear Bibilical Christianity. We're all well aware that if the "seeker" walks into a PCUSA congregation,there is no such guarantee.
In my own congregation I am a "liberal", because I believe that Catholics can be Christians and that religious artwork is not always idolatrous. I choose to belong to a body that is slightly more "fundamentalist" than I am, rather than one where people are asking, "You don't really believe that stuff, do you?"
As for the agonizing issue about when to "abandon" a church or seminary to liberals, I don't have an easy answer to that one. I became a Christian in the 90's, so I don't have personal or family history that binds me to one of the mainline churches. I believe that there is a point when the only option is to leave, but all I can do is pray for believers who are wrestling with whether their own church has reached that point. I do note, however, that if enough orthodox Presbyterians had followed Machen out of the "mainline" church, Bibilical orthodoxy would now be the "mainstream" of Presbyterianism, and the neo-Unitarians would now be the "splinter group."