How to Plot Phase Response of Discrete Time Fourier Transform (DTFT)?

I have implemented the DTFT in a MATLAB function.The function takes the array of values and the starting index as its arguments.

function[X]=DTFT(x,n)
syms w
l=length(x);
n_=n:l+n-1;
e=exp(-1j*w*n_);
X=sum(x.*(e));
end

I have implemented the DTFT function with the following code :

 x=[2 1 0 1 2];
 hold on
 subplot (1,2,1) ;ezplot(abs(DTFT(x,-2)));
 title('DTFT of Original Signal');
 subplot(1,2,2); ezplot(angle(DTFT(x,-2)));
 title('Phase Response of Original Signal');

As per the book, the magnitude of the DTFT is correct; however, the phase response should be zero for the symmetric array of x given above, which isn't the case.

How do I get the proper zero phase response/What am I doing wrong here?