I'm trying to write "this is not a praise/compliment." I consulted my friend about it and he said I wrote "I'm not praising you!" Like I'm being defensive... what do you think?
The expression 褒めてねえぞ would be used following a statement which the other party could have misinterpreted criticism as praise and you want to clarify your intent. In this sense, it can seem defensive.
「褒め言葉じゃないんですが、」 or 「褒めてるわけじゃないけど、」 would seem more appropriate if you want to lead your sentence with 'This is not praise/a compliment'.
Without more context, it would be difficult to tell whether this would be the most appropriate expression to use.