What is forbidden of the Da‘wah of the Period of Ignorance

Narrated Jabir:

We were in the company of the Prophet in a Ghazwa. A large number of emigrants joined him and among the emigrants there was a person who used to play jokes (or play with spears),
so he (jokingly) stroked an Ansari man on the hip. The Ans-ari got so angry that both of them called their people. The Ansari said, "Help, O Ansar!" And the emigrant said "Help, O emigrants!" The Prophet came out and said, "What is wrong with the people (as they are calling) this call of the period of Ignorance? "Then he said, "What is the matter with them?" So he was told about the stroke of the emigrant to the Ansari. The Prophet ﷺ said, "Stop this (i.e. appeal for help) for it is an evil call. "Abdullah bin Ubai bin Salul (a hypocrite) said, "The emigrants have called and (gathered against us),
so when we return to Medina, surely, the more honorable people will expel therefrom the meaner," Upon that 'Umar said, "O Allah's Prophet! Shall we not kill this evil person (i.e. Abdullah bin Ubai bin Salul) ?" The Prophet) said, "(No), lest the people should say that Muhammad used to kill his companions."

حَدَّثَنَا مُحَمَّدٌ، أَخْبَرَنَا مَخْلَدُ بْنُ يَزِيدَ، أَخْبَرَنَا ابْنُ جُرَيْجٍ، قَالَ أَخْبَرَنِي عَمْرُو بْنُ دِينَارٍ، أَنَّهُ سَمِعَ جَابِرًا ـ رضى الله عنه ـ يَقُولُ غَزَوْنَا مَعَ النَّبِيِّ ﷺ وَقَدْ ثَابَ مَعَهُ نَاسٌ مِنَ الْمُهَاجِرِينَ حَتَّى كَثُرُوا، وَكَانَ مِنَ الْمُهَاجِرِينَ رَجُلٌ لَعَّابٌ فَكَسَعَ أَنْصَارِيًّا، فَغَضِبَ الأَنْصَارِيُّ غَضَبًا شَدِيدًا، حَتَّى تَدَاعَوْا، وَقَالَ الأَنْصَارِيُّ يَا لَلأَنْصَارِ. وَقَالَ الْمُهَاجِرِيُّ يَا لَلْمُهَاجِرِينَ. فَخَرَجَ النَّبِيُّ ﷺ فَقَالَ " مَا بَالُ دَعْوَى أَهْلِ الْجَاهِلِيَّةِ ". ثُمَّ قَالَ " مَا شَأْنُهُمْ ". فَأُخْبِرَ بِكَسْعَةِ الْمُهَاجِرِيِّ الأَنْصَارِيَّ قَالَ فَقَالَ النَّبِيُّ ﷺ " دَعُوهَا فَإِنَّهَا خَبِيثَةٌ ". وَقَالَ عَبْدُ اللَّهِ بْنُ أُبَىٍّ ابْنُ سَلُولَ أَقَدْ تَدَاعَوْا عَلَيْنَا، لَئِنْ رَجَعْنَا إِلَى الْمَدِينَةِ لَيُخْرِجَنَّ الأَعَزُّ مِنْهَا الأَذَلَّ. فَقَالَ عُمَرُ أَلاَ نَقْتُلُ يَا رَسُولَ اللَّهِ هَذَا الْخَبِيثَ لِعَبْدِ اللَّهِ. فَقَالَ النَّبِيُّ ﷺ " لاَ يَتَحَدَّثُ النَّاسُ أَنَّهُ كَانَ يَقْتُلُ أَصْحَابَهُ ".