A statement every Agnostic should be able to agree with is that if Christianity is true, it is imperative that Christians spread it to as many people as possible. However, all too often, Agnostics tend to confuse "I don't know if Christianity is true" with "you don't know if Christianity is true". Therefore, while they themselves admit they do not know the truth value of Christianity, they can often be found obstructing the Gospel as aggressively, if not more so, than many atheists.
As a Christian, I know Christianity is true. Because I know it's true, up to and including the fact that outside of Christ, all will be condemned, I preach with both knowledge and love. I obstruct other beliefs not out of personal nor projected ignorance, but knowing the truth and recognising that which contradicts it. I attempt to spread my beliefs as far as possible for the benefit of those who hear it.
An Agnostic may object to the above paragraph, clinging to the strange idea that confidence is arrogance, and so I don't really know Christianity is true. Well, yes I do, but let's set that aside for a moment. You can only mean that Christians don't know it in two possible ways. On the one hand, you can claim Christianity is not true, and you know it. At that point, you are forced to become an atheist and contend with Christianity with your knowledge, not your feigned ignorance. Alternatively, you can say Christianity might be true, you just aren't sure. In this case, you should operate under the assumption that even if you do not believe yet, it is better to let Christians preach, just in case.
Let's imagine a scenario in which you are in a building that, supposedly, is on fire. The fire alarm goes off, and the fire crew go room to room, asking people to evacuate. Finally, they reach your room, and they start saying "Alright people, we need you to evacuate the building, there's a fire." What sort of numpty would you be if, not seeing fire or smoke, you told the fire crew "hold on, you don't know there's a fire, why should we go anywhere?" Would this not be extremely irresponsible of you? Even if you don't see the fire, even if you don't know what the fire crew know, even if you insist on staying in your seat at the possible cost of your own life, is it not actually very selfish of you to prevent the fire crew from saving other people's lives?
In much the same way, even if you do not see Hell, even if you do not know what Christians know, even if you insist on remaining an Agnostic at the possible cost of your own eternal soul, it is a great evil for you to hinder people who, for all you know, could be sparing their fellow man everlasting damnation.
As an Agnostic, there are only 3 sensible options. The first is to grow a spine and admit you believe Christianity is false. Drop the veneer of "tolerance" for all views and oppose Christianity as the lie you think it is. The second is to remain an Agnostic, not knowing Christianity is true, but not knowing it isn't either. At this point, it is vital that you step out of the way. Maybe even do yourself the favor of taking option 3: find out if Christianity is true (and it is), at which point you "join the fire crew", so to speak, and evacuate the building so people don't go to Hell. Obstructing Christianity like an atheist while pretending to be an Agnostic is not a logically coherent option.