The logical thing would be to contact the DbD support and ask why they banned you.
If they dont reply within a timely manner or refuse to tell you outright why (and show proofs of some sort), you can simply contact the steam support afterwards and basically either make them remove your bann or show you a valid reason why.
Obviously a ticket with "I banned, why?" or equal stupid stuff will not cut it.
Attach screenshots, use proper language and demand an answer.
You bought the game and even if you are (rightfully) banned, they still cant bann anybody without having a proper proof to do so.
Worst case, you are still banned,
middle case you and we know why you are banned,
best case your bann gets removed or superbest case Steam removes the rights to manualy bann users from DbD Devs. (Which legit happend with other devs, as they were manualy banning people for no valid reason)
Bottom line is, there is much more to win than to loose for anybody here that got banned recently.