No. If you have a guild claim, no one can destroy anything on it. Unless it is another guild, that is at war with you, and it is a JH now (turned off on MMO servers for now). That is a temporary mechanics, once we will implement Siege and Battle systems, guilds in wars will have to win a series of battles to downgrade a monument of their enemy and only THEN they will be able to siege it and potentially destroy.
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