What is the ruling on one who does not declare a disbeliever to be a disbeliever, and on one who abandons some Sunnahs out of fear?

Jews, Christians, Buddhists, and others from among the followers of religions other than Islam are all disbelievers. Their disbelief is known by necessity from the Islamic religion. And whoever denies their disbelief, or doubts it, or does not declare them disbelievers, is a disbeliever, because not declaring disbelievers to be disbelievers or doubting their disbelief is among the nullifiers of Islam. Judge Iyad said: "We declare as disbelievers whoever follows a religion other than the religion of the Muslims, or hesitates concerning them, or doubts, or validates their creed, even if he outwardly manifests Islam and believes in it, and believes in the invalidity of every creed other than it, then he is a disbeliever by manifesting what he manifested contrary to that." And in Al-Iqna' and its commentary: "Whoever does not declare as disbelievers those who follow a religion other than Islam, such as Christians and Jews, or doubts their disbelief, or validates their creed, is a disbeliever, because he is belying the statement of Allah Almighty: (And whoever desires a religion other than Islam, it will never be accepted from him, and in the Hereafter he will be among the losers)."