"Well, in my opinion this bike routes are likely to be informative and give a good clue for new riders in London like me... I have been many times riding along Walthamstow, Tottenham and other places, that's true these places have a bit of grafitty and junk yards around, but if you are going for a ride, it should be a pleasant time instead evaluating where you are ridding. I did enjoy riding at the north of Walthamstow, as this article made a few comments about the the animals around near the country side, for me that area was very pleasant to ride.
Make sure that you are mentally positive when riding your bike, in my thought I think it MUST be pleasant.
Many people have different opinions due to their experience, I would suggest if you don't like certain areas, try to avoid it and find out another routes more suitable to you. Remember, you are riding for pleasure...