No one's advocating executions...we're talking about excommunications. Most Christian countries don't execute people for ecclesiastical crimes anymore. Its one thing to say no you can't have communion, and quite another to chop off someone's head. So I am not sure why you are bringing up the melodramatic example of getting your head chopped off for being excommunicated. No one's going to get their head chopped off for being denied communion at present.
If the Church is going to say that you get excommunicated for committing a certain act, then the Church had better back it up otherwise people get the impression that the sin isn't a serious sin after all. Politicians particularly become emboldened by a lack of enforcement of these rules by the Church.