nested ifs are the devil. NO! Do flat non-nested ifs instead, by reversing the if-statement negation and exiting instead.

SetPointIan_BAD.cs

    //is called recursively to draw the beam of light
    public void SetPoint(Vector3 origin, Vector3 direction)
    {
        RaycastHit2D hit = Physics2D.Raycast(origin, direction);

        //hit something!
        if (hit.collider != null)
        {

            if (hit.collider.GetComponent<Switch>().passable == true )
            {

                switch (hit.collider.tag)
                {
                    case "Solid":
                        list.Add(hit.point);
                        break;
                    case "Reflect":
                        list.Add(hit.point);
                        Debug.Log("Re flect!!");
                        break;
                    case "Refract":
                        list.Add(hit.point);
                        Debug.Log("RE FRACT");
                        break;
                    case "Switch":
                        list.Add(hit.point);
                        Debug.Log(hit.collider.name);
                        break;
                    default:
                        break;
                }
                isOutsideScreen = false;

            }
            //hit nothing!
            else
            {
                list.Add(origin + direction * Screen.width);
                isOutsideScreen = true;
            }

        }

    }

SetPointIan_GOOD.cs

    //is called recursively to draw the beam of light
    public void SetPoint(Vector3 origin, Vector3 direction)
    {
        RaycastHit2D hit = Physics2D.Raycast(origin, direction);

        //hit nothing!
        if (hit.collider == null)
        {
            list.Add(origin + direction * Screen.width);
            isOutsideScreen = true;
            return;
        }

        //hit somethign
        else 
        {

            switch (hit.collider.tag)
            {
                case "Solid":
                    list.Add(hit.point);
                    break;
                case "Reflect":
                    list.Add(hit.point);
                    Debug.Log("Re flect!!");
                    break;
                case "Refract":
                    list.Add(hit.point);
                    Debug.Log("RE FRACT");
                    break;
                case "Switch":
                    list.Add(hit.point);
                    Debug.Log(hit.collider.name);
                    break;
                default:
                    break;
            }
            isOutsideScreen = false;

        }
    }