Listen to these sentences at the Talking People Podcast: Useful Language. Communicative Strategies 3
Defending a Position
I'm quite sure about this
I'll explain the reasons I have to believe this -- ...
Let me tell you my reasons -- ...
Let me explain -- ...
Let me see... How can I explain?
My point is this -- ...
That's why I believe (this or that)
That's the reason why I think (this or that)
I know because (reason)
I definitely know! I've been through that several times in my life
Well, what are YOUR reasons to believe that?
Well, the good thing about my point is ...
How can you deny that?
If you look at this figures carefully, I'm sure you will see...
Do you honestly think I'm wrong?
Well, that's what statistics say...
More...
Check out also "Agreeing", "Asking for Clarification and More Info", and "Disagreeing"
Please, for "defending positions" and "attacking positions", read my notes on Discussions in the TP Speaking section - Discussions
More: Agreeing and challenging opinions (read from Natural English)