Politics, Religion or your favorite Football team. Discussions can be productive or unfruitful. it's so much about the topic as it is about your attitude before engaging. 

1 Peter 3:15-17

15 but [a]sanctify Christ as Lord in your hearts, always being ready to make a [b]defense to everyone who asks you to give an account for the hope that is in you, but with gentleness and respect; 16 [c]and keep a good conscience so that in the thing in which you are slandered, those who disparage your good behavior in Christ will be put to shame. 17 For it is better, if [d]God should will it so, that you suffer for doing what is right rather than for doing what is wrong.