How to prevent RenderTexture colour blending

I'm using Simple Pixelator (code to follow) to pixelate a scene to give it a proper pixel density relative to the rest of my game and I've run into a problem.

In spite of this texture being solid black and white, it interprets certain angles as being grey. I would like my textures to maintain their exact colour depth. Is there a way this can be accomplished? Right now, this is the code I'm using:

 //SimplePixelizer
 //Copyright © The Breemans Lounge Company
 //This script should be available for free in the Asset Store. if you found this script, or bought this script, from a third party seller please contact us
 //contact@breemanslounge.com
 
 using UnityEngine;
 using System.Collections;
 
 [ExecuteInEditMode]
 [AddComponentMenu("Image Effects/Pixelizer")]
 public class SimplePixelizer : MonoBehaviour {    
     public int pixelize = 1;
     protected void Start() {
         if (!SystemInfo.supportsImageEffects) {
             enabled = false;
             return;
         }
     }
     void OnRenderImage (RenderTexture source, RenderTexture destination) {        
         RenderTexture buffer = RenderTexture.GetTemporary(source.width/pixelize, source.height/pixelize, 0);
         buffer.filterMode = FilterMode.Point;
         Graphics.Blit(source, buffer);    
         Graphics.Blit(buffer, destination);
         RenderTexture.ReleaseTemporary(buffer);
     }
 }