It is always with consent on an energetic level. You are within the frequency domain of this being, and therefore can connect with this being. You are both making the connection simultaneously. Telepathy is more like having the same exact thought at the same exact timing. If you're fearful of this, then you are a match to this lower vibration of thought and therefore you are giving consent by the very idea of "I hope this person does not telempathically/telepathically attack me." Raise your vibration. Then how could you be harassed by seemingly unwanted thoughts?