I am hanfi and not an expert in maliki fiqah.Maybe a malki would better answer this but I think the basic problem is this that dog is not najis in malkis
Dogs Are Pure in the Maliki Madhab
The Reported Opinion of Imam ‘Ikrimah and Malik ibn Anas (Rahimahumullah)
Imam Ash-Shawkaani (rahimahullah) states in his masterpiece “Nayl Al-Awtaar Sharh Muntaqaa Al-Akhbaar” the following below the following narration of the Prophet Muhammad,
“From Abu Hurayrah who said that Rasulullah (alayhis salaam) said, “When a dog licks one of your vessels (e.g. bowl), apply dirt to it and then wash the vessel seven times.” ((This narration is reported by Imam Muslim in his Sahih 89/279 as well as by An-Nasaa’i hadith number 66 ))
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[Says Shawkaani]: And this narration also proves that the dog is najaasah (impure)…and the Jumhoor (majority) hold this opinion. And ‘Ikrimah and Maalik in a report from him state “Verily it is Taahir (pure)”. And their proof is the statement of Allah ta’alaa,
فَكُلُواْ مِمَّا أَمْسَكْنَ عَلَيْكُمْ وَاذْكُرُواْ اسْمَ اللّهِ عَلَيْهِ وَاتَّقُواْ اللّهَ إِنَّ اللّهَ سَرِيعُ الْحِسَابِ
(Say: lawful unto you are (all) things good and pure: and what ye have taught your trained hunting animals (to catch) in the manner directed to you by Allah ”eat what they catch for you, but pronounce the name of Allah over it: and fear Allah; for Allah is swift in taking account.” (5:4)
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Also another proof is what is established in Abu Dawud from the hadith of Ibn ‘Umar with the words, “Dogs would come freely into the masjid and urinate in the time of the Rasulullah (‘alayhis salaam), and they would not pour water over it (i.e. the urine).” (Sahih Al-Bukhari hadith number 174 in the Book of Wudhu’)
[Note that Ibn Hajr states this occurred before doors were put on the masjids and the command to keep them clean was established. Though this is the opinion of a Shafi'i and not that of the Maalikis] – End quote from Nayl Al-Awtaar.
The Shafi’i Judge and Jurist Qadhi As-Safadi states, “Malik says that dogs are pure and what they lick is not made impure, but that a vessel licked by a dog should be washed to avoid filth.” ((Taken from “The Mercy in the difference of the Four Sunni Schools of Islamic Law” translated by ‘Aa’ishah Bewley printed by Dar-al-taqwa. Page 4 ))
The following quotes are statements from Imam Maalik as reported in the Mudawwanah of Imam Maalik regarding the dog:
“One may eat what it catches in a hunt, how then can we declare Makrooh (hated or disliked) what it drinks (or places its tongue in).” (page 116)
Maalik said, “If one desires to make wudhu’ from a vessel wherein a dog has drank (or put its tongue in), it is ok for him to make wudhu’ from it and pray.” (pg 115)
Maalik said, “If a dog puts his tongue in a vessel of milk (labn) there is no harm (la ba’as) if one takes (i.e. eats) from that milk.” (ibid)
Note that there are many other quotes from him within Volume 1 of the Mudawwana regarding the purity of the dog. I have chosen these only as a sample. [Vol. 1 published by Daar Al Kutub Al-'Ilmiyyah published in 2005 CE]
The Maliki Faqih (jurisconsult) of Andalus, Ibn Rushd states in his “Bidayatul-Mujtahid”,
“Maalik held the view that the leftover of a dog is to be spilled and the utensil is to be washed, as it is a ritual act of non-rational worship, for the water that it has lapped up is not unclean (najas). He did not require, according to the widely known opinion from him, the spilling of things other than water, which a dog had licked. The reason, as we have said, is the conflict with analogy according to him. He also believed that if it is to be understood from the tradition that a dog is unclean, it opposes the apparent meaning of the Book, that is, the words of Allah ta’alaa, “So eat of what they catch for you…” meaning thereby that if the dog had been unclean the prey would become unclean by the touch of the dog’s (mouth). He supported this interpretation by the required number of washings, as number is not a condition in the washing of unclean things. He held that this washing is merely an act of worship. He did not rely upon the remaining traditions as they were weak in his view.” (pg 27 published by Garnet; also see Al-Hidayah of Imam Al-Ghumaari Vol. 1 page 288 for a detailed discussion of the chains of narration)