Even only hearing about Islam is not Enough. Do we investigate everything we hear by name? For example, we heard of Shamanism; how many of us actually made research on Shamanism in detail?

Just hearing "Islam" is not enough for being responsible. In western countries, people hear about Islam everyday from media, but they hear in a negative way. They hear a different, violent, bloody religion which is actually not Islam. If they become enemies of Islam, are they going to be responsible of their hatred?

Allah never says that he is going to punish people just after hearing Islam. He never says something like this:

You heard about Islam. Why didn't you research it? You deserved my punishment for your ignorance and laziness!

But, he says that he will say something like this:

قَالُوا أَوَلَمْ تَكُ تَأْتِيكُمْ رُسُلُكُم بِالْبَيِّنَاتِ قَالُوا بَلَى قَالُوا فَادْعُوا وَمَا دُعَاء الْكَافِرِينَ إِلَّا فِي ضَلَالٍ

They will say, "Did there not come to you your messengers with clear proofs?" They will say, "Yes." They will reply, "Then supplicate [yourselves], but the supplication of the disbelievers is not except in error."

Mumin/Ghafir 50 (40/50)

From another ayat:

وَلَقَدْ أَهْلَكْنَا الْقُرُونَ مِن قَبْلِكُمْ لَمَّا ظَلَمُواْ وَجَاءتْهُمْ رُسُلُهُم بِالْبَيِّنَاتِ وَمَا كَانُواْ لِيُؤْمِنُواْ كَذَلِكَ نَجْزِي الْقَوْمَ الْمُجْرِمِينَ

And We had already destroyed generations before you when they wronged, and their messengers had come to them with clear proofs, but they were not to believe. Thus do We recompense the criminal people

Yunus 13 (10/13)

Another:

لَمْ يَكُنِ الَّذِينَ كَفَرُوا مِنْ أَهْلِ الْكِتَابِ وَالْمُشْرِكِينَ مُنفَكِّينَ حَتَّى تَأْتِيَهُمُ الْبَيِّنَةُ

Those who disbelieved among the People of the Scripture and the polytheists were not to be parted [from misbelief] until there came to them clear evidence

Beyyine 1 (98/1)

Another:

حَقِيقٌ عَلَى أَن لاَّ أَقُولَ عَلَى اللّهِ إِلاَّ الْحَقَّ قَدْ جِئْتُكُم بِبَيِّنَةٍ مِّن رَّبِّكُمْ فَأَرْسِلْ مَعِيَ بَنِي إِسْرَائِيلَ

[Who is] obligated not to say about Allah except the truth. I have come to you with clear evidence from your Lord, so send with me the Children of Israel."

Araf 105 (7/105)

Another:

قَالَ يَا قَوْمِ أَرَأَيْتُمْ إِن كُنتُ عَلَى بَيِّنَةٍ مِّن رَّبِّيَ وَآتَانِي رَحْمَةً مِّنْ عِندِهِ فَعُمِّيَتْ عَلَيْكُمْ أَنُلْزِمُكُمُوهَا وَأَنتُمْ لَهَا كَارِهُونَ

He said, "O my people have you considered: if I should be upon clear evidence from my Lord while He has given me mercy from Himself but it has been made unapparent to you, should we force it upon you while you are averse to it?

Hud 28 (/28)

And so on...

The word is: بينة

Meaning: clear evidence

You can make a search on this word in Quran. Quran is full of this word. Investigate how it is used, and how much it is important. You will see that only the ones who see the clear evidence are to be responsible. Just hearing is not enough to make you responsible. Hearing in TV can make negative effect as it does in western countries. If you hear Islam from someone else, you hear as much as that person is able to explain to you. You need to see a clear evidence to be responsible of what you saw.