"I don't agree!" 

"Don't say that some people are not so easily  convinced!" 

Like this everybody, used to disagree, at some times! 

One should not expect that others should be easily  convinced. 

It always depends on 
'how we convey', 
'how we act', 
'how we react', 
'the time', 
'the circumstances', 
'the situations', 
'the mood', 
'the relationship', 
'the message', 
'the necessity' and so on. 

You say, "Two plus Two comes Four". 

Your friend is not convinced. 

Do you, 'argue', 'fight' or 'try to convince him', 
at any cost? 

If you are 'sure' on you, 
then you won't do. 

It is absolutely not necessary to do so! 

If you are 'not sure' on you, 
then only you will do. 

It is not the matter that, 

"Why people are not convinced?" 

"Why SOME people are not convinced?" 

"Why some people are not SO EASILY  convinced?" 

This is the matter, 

Let us ask us, 'why we are not convinced?' 

Let us try to convince us! 

Let us get convinced! 

Let us convince our life!