Clutter is in the eye of the beholder. Your landlord says it's bad, you say it isn't. Unfortunately, your landlord has the leverage. He can evict you for creating a hazard and then what do you do with an eviction on your record.
I can't say whether you're right or wrong without seeing the room. If you can figure out how to post a photo of the room, you'll get some opinions one way or the other. If you can't figure out how to post one here, there are a couple of other legal websites (thelaw dot com is one) where you can upload a photo into your post.

