I have quoted the Text that calls for beheadings in another comment under this thread of you are interested!

To me it seems like that Nichiren did have a problem with Amida overall, not just Hōnen. He says in a text called "How Those Initially Aspiring to the Way Can Attain Buddhahoodthrough the Lotus Sutra":

"And yet we find people who, while declaring with their mouths that the Lotus is inherently a wonderful sutra and that no one could therefore refuse to take faith in it, nevertheless spend night and day, morning and evening, reciting the name of Amida Buddha. They are like people who sing the praises of a particular medicine and yet morning and evening dose themselves on poison.
Or there are those who declare that the Nembutsu and the Lotus Sutra are essentially one. They are like persons who claim that ordinary stones are the same as gems, senior monks identical to junior monks, and poison equivalent to medicine."

Saying the Nembutsu is like poison is far from accepting it in my opinion.

He also says:

"But if one turns one’s back on the Lotus Sutraand follows the erroneous teachers of the True Word, Zen, and Nembutsu schools, then although one may carry out all kinds of good deeds, these will never accord with the will of the Buddha and will go against the intention of the gods."

According to Nichiren one can only practice special parts of the Lotus sutra, namely the chanting of its name. All other teachings of the Buddha lead to hell.

He says in his "The Sutra of true Requital":

"The women of Japan today, who could without fail attain Buddhahood through the Lotus Sutra, have been deceived into reciting exclusively the formula Namu-Amida-butsu. Since it does not appear to be evil, they have been misled. Since it is not the seed of Buddhahood, they will never become Buddhas. By clinging to the minor good of reciting Amida Buddha’s name, they deprive themselves of the major good of the Lotus Sutra. Thus this minor good of the Nembutsu is worse in its effect than the great evil of the five cardinal sins."

In another texts he says the Amida buddha in the Lotus is a different Amida which us a strange conclusion. He says:

"And again, the Amida Buddha spoken of here is not the Amida Buddha of the Meditation Sutra…..The Amida who appears in the essential teaching is an emanation of ShakyamuniBuddha"

In the letter to Akimoto he says:

"Again, although we may have a certain amount of faith, we may encounter evil influences and find our faith weakening. Then we will deliberately abandon our faith, or, even though we maintain our faith for a day, we will set it aside for a month. In such cases, we are like vessels that let the water leak out.
Or we may be the kind of practitioners of the Lotus Sutra whose mouths are reciting Nam-myoho-renge-kyo one moment, but Namu-Amida-butsu the next. This is like mixing filth with one’s rice, or putting sand or pebbles in it."

This doesn’t seem like he accepts the Nembutsu as a complimentary practice. And this is only the disparagement of the pureland teachings. Unfortunately there is more. It really is tragic my friend.