There is an element to Autism/Aspergers whereby someone could have Space and/or Touch issues. I know of some who either stand too close, hate someone standing too close and also barging through gaps between people that they cannot get through.
Some inappropriate behaviour, like this can be unknown to the person doing it, just like saying the wrong thing and inadvertently not realising that the words are hurtful.
There are also elements of cultural differences too that may be unknown/unused to others e.g. French people kissing others on each cheek as a friendly gesture.