Security risk of Enabling MS DTC Distributed transaction?
The more features you turn on, the greater the risk.  The Linux community openly says to turn features off if you don't need them.  Microsoft has a Windows Server 2012 core mode:

Install Server Roles and Features on a Server Core Server

I don't see DTC on the list.  There are good practices, but if there is a business need I turn it on.  I always say the right tool for the right job.  But you can change the default port for DTC, if you do this hacker scanning tools won't find it. 

How to Configure MSDTC to Use a Specific Port in Windows Server 2012/2012R2

I have worked at banks that change the default port of all the SQL Servers.  In some cases, each server had a port in a range of 100 and all the firewalls let that group through.  It is a support nightmare, but it is VERY secure.