Are maltheists still Christians since they believe God exists?

Maybe, maybe not!

CHRISTIAN – A follower or believer in Jesus Christ.

But Christianity broke away from Judaism and the whole of the old testament is Judaic. The God worshipped by Chrsitians is the Judaic one! Similarly Islam is just a badly rewritten version of Chrsitianity and worships the same Judaic god!

So maltheists can be of any of the three!

The one thing they cannot be is atheist!

Maltheists believe that God exists, but is evil.

Simply believing God exists does not make someone a Christian, and no Christian believes God is evil.

Why, even the demons believe that there is one God - they believe that and they shudder because they know what their punishment will be (James 2:19). Demons, like maltheists, are not Christians.

Everyone who seeks God has to assume that God exists and that He is good and that He wants us to seek Him.

No. Christians are committed to Christ

It doesn't mean that they are christian, they could be, they could not be, but they are certainly a theist.