The one who reviles the Muslims and praises the kuffaar is on the edge of disaster

Allah, may He be exalted,
has instructed His believing slaves to love one another and to take one
another as friends, and He has instructed them to hate His enemies and regard
them with enmity for the sake of Allah. He has stated that friendship can
only be among the believers and enmity is to be between them and the
kaafirs; disavowing them is one of the basic principles of their faith and
is part of perfecting their religious commitment. There are very many
verses, hadeeths and comments of the early generation to that effect. 

For example, Allah, may He
be exalted, says (interpretation of the meaning): 

“O you who believe! Take
not the Jews and the Christians as Auliya (friends, protectors, helpers,
etc.), they are but Auliya to one another. And if any amongst you takes them
as Auliya, then surely he is one of them. Verily, Allah guides not those
people who are the Zalimoon (polytheists and wrongdoers and unjust)”

[al-Maa’idah 5:51] 

“Verily, your Walee
(Protector or Helper) is Allah, His Messenger, and the believers, – those
who perform As-Salat (Iqamat-as-Salat), and give Zakat, and they bow down
(submit themselves with obedience to Allah in prayer).

And whosoever takes
Allah, His Messenger, and those who have believed, as Protectors, then the
party of Allah will be the victorious.

O you who believe! Take
not for Auliya (protectors and helpers) those who take your religion for a
mockery and fun from among those who received the Scripture (Jews and
Christians) before you, nor from among the disbelievers; and fear Allah if
you indeed are true believers”
[al-Maa’idah 5:55-57] 

The Prophet (blessings and
peace of Allah be upon him) explained that love for the sake of Allah and
hate for the sake of Allah are among the signs of faith. Abu Dawood (4681)
narrated from Abu Umaamah (may Allah be pleased with him) that the Messenger
of Allah (blessings and peace of Allah be upon him) said: “Whoever loves for
the sake of Allaah and hates for the sake of Allaah, gives for the sake of
Allaah and withholds for the sake of Allaah, will have perfected his faith.”

Classed as saheeh by
al-Albaani in Saheeh Abi Dawood 

Al-‘Allaamah Abu’t-Tayyib
Siddeeq ibn Hasan al-Bukhaari (may Allah have mercy on him) said in
al-‘Ibrah (p. 245): 

As for the one who praises
the Christians and says that they are people of justice or that they love
justice, and often speaks highly of them in gatherings and speaks ill of the
sultan (Muslim ruler) and the Muslims, and attributes justice to the kuffaar
and says that they are free of injustice or oppression, the ruling on
the one who praises them in this manner is that he is an evildoer who is
disobeying Allah and committing a major sin, from which he has to repent and
regret it, if he praises the kuffaar themselves regardless of the kufr
(disbelief) that they follow. But if he praises them because they are
disbelievers, then he is also a kaafir because he has praised the kufr that
they are following. 

Shaykh ‘Abd ar-Rahmaan
al-Barraak (may Allah preserve him) said: 

The one who believes that
the Jews and Christians are following a sound religion is a kaafir, even if
he follows all the laws of Islam, and he is rejecting the general meaning of
the message of the Prophet (blessings and peace of Allah be upon him). 

Based on that, mentioning
the good qualities of the kuffaar by way of praising, admiring and
respecting them, is haraam because that is contrary to the rulings of Allah
concerning them. End quote. 

Indeed, Imam an-Nawawi (may
Allah have mercy on him) said, discussing the phrases that constitute
apostasy: 

If a teacher of boys says:
“The Jews are much better than the Muslims, because they give the one who
teaches their boys all his rights,” he has become a kaafir thereby.

End quote from Rawdat
at-Taalibeen, 10/69 

If, along with reviling the
Muslims and praising the kaafirs, he also wishes that he was one of them,
then he is a kaafir who has gone beyond the pale of Islam. He should be
asked to repent and he should be taught his religion; if he repents (all
well and good), otherwise he is to be executed as an apostate by the ruler. 

See also the answer to
question no. 6688 

And Allah knows best.