Let me put a bit of a different perspective on this.

IF we had a multi-party system like, for example, Israel, it would be easier for people with widely divergent viewpoints to sort themselves out.

These days, particularly with incessant media coverage exaggerating things, we have a number of issues which polarize people...environmental claims, abortion, gun control, 'globalization', immigration... add your own to the list.

Now, when conservative extremists on any issue need a platform and want to elect legislators who reflect their views, they 'sometimes' try to form a party, but usually it is easier to just use a ready-made entity and co-opt it for their own purposes.. (kinda like 'folk' being handy for shoving all sorts of music into).
It is obvious that those flaky Democrats won't be very receptive...*grin*....so they congregate in the Republican party and often scare/convince/intimidate 'moderate' Republicans to agree on a number of issues. Then, when the far right needs a candidate who will further their agenda, they make it clear that, in order to get even basic Republican views supported, the whole party must adapt and adopt more extreme views than it might (and than it did 30, 40, 50 years ago) otherwise.

There are mindsets...(and we can argue forever where they come from)... that seek 'power for its own sake', and which have narrow, intolerant views of ideas other than their own, and which have few compunctions about methods (including lies and inconsistent logic) to get what they want...like Machiavelli explained long ago.
   Sometimes there are even deviant personalities (Hitler is the 'common' recent example) who combine hate with a certain cleverness and move entire nations into paths of destruction..... and the party they choose, when they can't easily create one, is the most 'conservative' party they can find. ((Where do you think Karl Rove and Dick Cheney would have landed if they had been born in Europe in the early 20th century?!!))

So...it is not exactly being 'Republican' that is the problem and that prompted the concerns that started this thread, but the way in which 'Republicianism' has been corrupted and co-opted by those with no scruples about how to push special interest agendas.

This is perhaps an over-simplified analysis...but it IS clear that this is NOT the Republican party *I* had friendly, meaningful dialogue with 40-50 years ago.