Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Indeed Dawah (calling towards Allah and His religion) is the mission of this Ummah (nation) for it is regarded as the best of nations. Allah says: "You [true believers in Islâmic Monotheism, and real followers of Prophet Muhammad (SAW) and his Sunnah (legal ways, etc.)] are the best of peoples ever raised up for mankind; you enjoin Al-Ma'rûf (i.e. Islâmic Monotheism and all that Islâm has ordained) and forbid Al-Munkar (polytheism, disbelief and all that Islâm has forbidden), and you believe in Allâh." (Aali Imran 3:110)"
The Prophet (Sallallahu Alaihi wa Sallam) used various methods in his Dawah which suited to the situation he addressed, and which produced good results. So, basically all methods of Dawah are lawful unless they contradict Shariah rulings. Therefore, the one who denies some methods or means of Dawah has to provide the evidence for his claims not the one who uses them.
No doubt, the internet is a useful means to serve Islam and provide Dawah effectively. It is a useful tool to spread Dawah especially those to whom Dawah cannot be given personally. Its benefits are so clear that they do not need to be mentioned here and no one can deny them. May be the person who mentioned wanted to recruit yow to engage in personal meetings for Dawah.
It is a known fact that there are unauthentic and weak Ahadith which are not proved. Scholars have published books distinguishing between authentic and unauthentic Ahadith and giving rulings about sound and weak Ahadith for a long time. The following Hadith of the Prophet (Sallallahu Alaihi wa Sallam) indicates that some people will tell lies about the Prophet (Sallallahu Alaihi wa Sallam). The Prophet (Sallallahu Alaihi wa Sallam) said: "Whoever intentionally lies about me will find his abode in the Hell-fire." (Bukhari and Muslim). So, it is useless for one to deny these facts given all the books of Hadith, and its sciences and the Fatawa of Imams and Muhadditheen who devoted their lives to this matter and wrote huge volumes in this subject.
Allah knows best.