"The client is literally screaming at me"

Life is too short to take abuse like that.  They have income and as noted above, someone is going to have to pay some tax on the gain.  The last client that acted like that with me because of a sizable tax due, became a former client once I hung up the phone.  

Trying to use a softer approach than Bob's I will add a simple suggestion.  Stick to what you do well and leave things you aren't comfortable with to other preparers.  Years ago I decided there were some areas that I wasn't going to mess with so to this day I have no problem telling clients or potential clients thanks, but no thanks.