这主要和作者想表达的意思有关。用someone 表示某个范围内的某一个不确定的人。如果用anyone，它的含义在一定语境从逻辑上看不一定是事实。譬如有些情况下，你不能强迫所有人服从。但有些情况下就会有这个可能。 这取决于说话人要表达的意思。你即使查语法书，语法书也只能解释someone 通常不用于否定句作宾语。应该有通常二字，也就是说不是绝对的。这道题如果不考虑语境，选anyone 也是对的。

语法是解释语言的。有些语法规则是灵活的，不是一成不变的。

请看几个外媒例句：

用someone:

1. You can't ask someone to babysit you on a Saturday. 

2. We can't ask someone to risk suffering what I went through.

3. I can't ask someone else to do that.

用anyone:

1. You can't force anyone to believe in God or not.

2. We can't force anyone to fight with us.

3. I can't force anyone to open his/her heart to me.