The game is actively enabling you to stop him by the overwhelming choice of helipads you have to choose from. Most maps have more than 5-8+ to choose from. Due to the very nature of EC, people will always eventually find spawn locations, which are protected by AAA. Add to this part of the EC objective is to advance into new zones and take the majority of the map, people are going to naturally stray across into an airbase.
Its the same situation of someone loitering near a base in Air RB or rushing a spawn point in Ground RB. There will always be those that do it and there is no way to reasonably stop every instance of it from happening without blocking off whole areas of the map for one team, which is counterproductive in many other ways and is not how the game functions.
Plus as I said, if someone is near one of your bases in Heli EC, do not spawn there. It is your choice to spawn there knowing someone is waiting....
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