Allies apostles trying to convert my cities.

[tryonedustbiter]

I accepted a deal which included making my neighbor an ally. A few turns later, there are a dozen apostles crossing our border. I went in to tell him to stop converting my cities and there is no option to do that.

You cannot tell your ally to back off and stop converting your cities. That makes an alliance not worth the paper it is printed on (metaphorically of course).

[Magma Dragoon]

Even if they aren't an ally, they don't honor a promise to stop spreading their religion, and you get no recourse or casus belli for this and they don't appear to suffer any diplomatic consequences. All you can do is denounce if you haven't already. Also the AI cheats REALLY hard even on emperor, so it's not unusual for the religiously inclined AIs to have like 15 apostles at once.

[Name Lips]

That's because the game doesn't view spreading religion as a hostile act, no matter what we as players might think.

[MarkJohnson]

I know, I have a small contenent start, I have Norway just find me and I agreed to a couple of request to keep him on my good sidse, a few turn later I scroll to the top most part of my map and see a swarm of apostles and missionaries already swarmiing my cities. I swear they teleported as they got there so fast.

Here's a screenshot:
http://steamcommunity.com/sharedfiles/filedetails/?id=804614607

[Sandor]

Use inquisitors to defend,they are cheap and get a huge+35 home territory bonus.

[Dray Prescot]

That is why I do not let other Civs visit my capital early in the game. If they do not know where you are, they can not send things to bother you, until they discover your location on their own.

[The_Pastmaster]

Originally posted by Magma Dragoon:

Also the AI cheats REALLY hard even on emperor

It's supposed to do that on higher difficulties. >_< Is it lazy? Yes. But higher difficulty = more bonuses to AI.