How to delete an object if there is another object of the same type at that position ?

Hi,I am doing a simple randomGeneration,my generation code works fine but it has a tendency to spawn more than 1 tile at a give position so i have made the script below to delete the gameobejects if another one of their kind is at their position,but it doesn't work it deletes non overlapping objects aswell.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class DestroyOnTouch : MonoBehaviour {
     public List<GameObject> walls = new List<GameObject>();
     public List<GameObject> tiles = new List<GameObject>();
 
     void Start () 
     {
         Invoke ("Destroy",2f);
     }
 
     void Destroy()
     {
         walls.AddRange(GameObject.FindGameObjectsWithTag("Walls"));
         tiles.AddRange(GameObject.FindGameObjectsWithTag("Tile"));
 
         StartCoroutine(DestroyWalls());
         StartCoroutine(DestroyTiles());
     }
 
     IEnumerator DestroyWalls ()
     {
         yield return null;
         for(int c = 0; c < walls.Count; c++)
         {
             for(int y = 0; y < walls.Count; y++)
             {            
                 if(c > y || y > c)
                 {
                     //yield return new WaitForSeconds(0.1f);
                     if(walls[c].transform.position == walls[y].transform.position)
                     {
                         Destroy(walls[y],0.1f);
                         walls.Remove(walls[y]);
                     }
                 }
             }
         }
     }
 
     IEnumerator DestroyTiles ()
     {
         yield return null;
         for(int c = 0; c < walls.Count; c++)
         {
             for(int y = 0; y < tiles.Count; y++)
             {            
                 if(c > y || y > c)
                 {
                     //yield return new WaitForSeconds(0.1f);
                     if(tiles[c].transform.position == tiles[y].transform.position)
                     {
                         Destroy(tiles[y],0.1f);
                         walls.Remove(tiles[y]);
                     }
                 }
             }
         }
     }
 }