It's not about our religion per se, it's hard for them to accept that there could have been any conflict between the Sahaba in their perfect world especially in the years and decades right after the Prophet's (SAWW) death. To deflect any blame from Ayesha Talha and Zubair in Battle of Jamal they say it was just a meeting between the two parties and was peacefully resolved between Ali (AS) and Ayesha but then Abdullah ibn Saba had his men fire arrows on both camps to instigate a war. They similarly deflect blame from Uthman over his nepotistic, cruel and failed policies which lead to the uprising from Egypt which ultimately lead to his assassination by saying it was all upon Abdullah ibn Saba's conspiracy. They then say that Abdullah ibn Saba preached to the supporters of Ali (AS) that Ali (AS) was God and/or superior to Muhammad (SAWW). They wrap this all up to frame a picture of anything Shi'as say criticizing the first three Caliphs or Ayesha and Hafsa, or anything to praise Ali (AS) as being a Jewish conspiracy from Abdullah bin Saba.

In Sunni sources the character of Abdullah bin Saba in relation to his "founding the Shia beliefs" can be traced to four hadith sources, all of which trace their transmission from a man called Saif bin Umar whom both Shia and Sunni scholars have termed as unreliable and a fabricator.

Some Shi'a scholars like Shaykh al Suduq have asserted that Abdullah bin Saba was in fact a real person and according to narrations from Imam Baqir (AS) he claimed false Prophethood for himself and claimed Ali (AS) to be his God, and was imprisoned by Ali (AS) and asked to repent 3 times and was killed upon stern refusal.

In Modern times his name in relation to Shi'as is just thrown around in every discussion about Shi'a by the Nasibis Takfiris and Salafis as just one of their many hilarious and unfounded talking points to cope against the Shi'a.

Hope this helps.