Assalamu alaikum wa rahmatullahi wa barakatuhu
About Mawlana Jalal Al-Din Ar-Rumi
Mawlana Jalal al-Din al-Rumi (d. 672) was the son, father, and grandfather of great Sunni Hanafi Jurists, teachers, and qadis, originating from Balkh or Kabul and settled in and around Istanbul. Ibn Hajar al-`Asqalani in al-Durar al-Kamina (1:352) cites him as "Mawlana" in the vibrant notice on his son Baha' al-Din Ahmad, known as Sultan ibn Mawlana, "one of the Imams of the Hanafi Masters, the brilliant, ascetic, pious Faqih, Usuli, and grammarian who trod the path of his father in leaving the world behind."
Mawlana's full name is Muhammad ibn Muhammad (ibn Muhammad) ibn al-Hasan ibn Ahmad ibn Qasim ibn Habib ibn `Abd Allah ibn `Abd al-Rahman ibn Abi Bakr al-Siddiq al-Hashimi. Hajji Khalifa said in Kashf al-Zunun (1:367): "He was a thoroughly knowledgeable Imam in Fiqh according to the School of Abu Hanifa - Allah be well-pleased with him - and he was knowledgeable in the science of juridical differences, then he devoted himself to worship exclusively. Miraculous gifts (karaamaat) are mass-transmitted from him. Allah have mercy on him."
He is known in the West as a "mystical" poet, mostly because of the translation of his large Persian book of poetry of singular beauty, the Mathnawi.
As for the claim that "He invited people to the Aqeedah of Wahdat-ul-Wujoud and to the Aqeedah of the oneness/unity of all religions", then Allah Most High said, {Say: Bring your proof if you are truthful} and He said, {O you who believe! If an evil liver bring you tidings, verify it, lest you smite some folk in ignorance and afterward repent of what you did}.
As for the statement "being a sufi, he is from among those who have gone astray in the history of Islam" it would be fair to say that this statement constitutes kufr because it attributes misguidance to the massive majority of the elite of this Umma.
It is a sign of the Divine power that Allah makes many purported disbelievers love and respect this Friend of Allah -- Jalal al-Din Rumi -- over seven centuries after his death while He makes some purported Muslims attack him and reveal themselves as corrupt enviers and friends of Shaytan.
Mawlana Jalal al-Din al-Rumi (Allah be pleased with him) said:
A sober-minded man said to Jesus,
"What in this existence is hardest to bear?"
"O dear soul," he replied, "the hardest is God's anger,
from which Hell is trembling as we are."
"And what is the protection against God's anger?"
Said Jesus, "To abandon your own anger at once."