It is the Landlords responsibility to maintain, improve or up-keep his property, not the tenants.

The only responsibility of the tenant has is to avoid damage to the premises, pay rent according to a lease agreement, avoid damages to the property and pay a security deposit in case there are damages AFTER YOU VACATE THE DWELLING.

You are also required to pay this security deposit for if, when or such time that a court of law, determines that you are liable for damages to the dwelling or property. Otherwise, you are not responsible or subjected to these demands before-the-fact.

If a judge determines that you have damaged the carpet; not the landlord, the security deposit can and will be retained by the landlord. However, it is the judge that will determine any reasonable amounts that should be paid for the carpet or damages, i.e. if you have damaged one room, you cannot be held liable for recarpeting an entire dwelling or pay inflated or unreasonable amounts of "undocumented" expenses or costs when the carpet can be cleaned instead of replaced.

This is why it is best to take "before" and "after" pictures to allow a judge to make the decision if you are held liable.

In other words you are correct in your assessment of this situation. This is wrongful and unethical behavior on the part of the landlord.

Additionally, you are in fact not responsible or liable for this carpet replacement and you are NEVER liable for IMPROVEMENTS to his investments, especially if this action is an arbitrary decision on the part of the landlord or you have had no legal eviction or you have no plans to vacate the dwelling or property.