Depending on how set somebody is I prefer and have had good results with a more diplomatic approach.
Acknowledge their fears/concerns as legitimate. Calling them an idiot, demeaning them will just make them hostile and defensive. Ask them about their concerns fears and that may well bring up BDS or other liberal half-truths/legends. This is usually due to media representation, not a conscious effort at slander - here present them the facts in a direct and tactful manner.
Find what they are concerned about: the economy, jobs/industy, national defense, etc., and use that to your advantage.
One thing that I often do when talking with aquaintances is bring up the typical liberal line, but then say - but did you know - and then introduce the facts demonstrating the conservative approach. Don’t tell them what to think, but then ask them what they think.
Several of my friends, who were your typical college liberals have changed their views and it’s kinda funny to hear them defend gun ownership and our involvement in Iraq and Afghanistan now.
I agree; you should not call anyone an idiot, fool, unpatriotic etc...but you can cerainly frame your comments in such a way that those hold liberal beliefs may for good reason be deserving of such appealations. And I would not back away from calling Obama something like an “inexperienced charlatan,” Harry Reid a forlorn fool, Nancy Pelosi “her nastiness” or whatever provocative and sarcastic names come to mind. I think last night I may have called a certain Massachusetts congressperson “a piece of pus” or something equally awful. Another thing on names and personalities; If the comment is made that “you just hate every Democrat or liberal politician” it is easy enough to reply with a litany of “Blue Dogs” that you admire and quote the wisdom of the pre-Clinton Democratic Party estaqblishment such as Daniel Patrick Moynihan who noted that “the central conservative truth is that it is culture, not politics, that determines the success of a society. The central liberal truth is that politics can change a culture and save it from itself.” My liberal friend agreed wholehearedly with the first part of this statement when I quoted it to him but looked quite perplexed when he tried to digest the second part. So much for liberal intellectual superiority.