Most anti tank missils cannot be fired from inside bldgs. but the challenge of the game allowing them to work outside of buildings in towns was terrible. you could never get them to work.
In real life it would be a team quickly coming out of or from behind a building firing and them moving back to cover.
So they decided to just allow the things to fire from inside buildings to have them available since anything outside of buildings was generalluy getting exposed way too long.
Its a game, things have to be comprimised at times.
Plus how often are they going to fire a weapon like that at infantry. Real world, not often. In game all the time.