Actually El Salvador government didn't push their citizens to use bitcoin, everyone have their own choice, those people should not did that. In my point of view, those people did criminal activity by destroying Bitcoin ATM, I personally think that what they did wasn't just that but actually they trying to destroy El Salvador's good economic future. Maybe they have some USD and don't want to suffer financial loss. That's so selfish, sacrificing many people's good future for their interest. That's my opinion.
Even if someone has US Dollar funds with him/her, how he is going to suffer losses if Bitcoin is also made the legal tender? USD usage will be largely unaffected. Those who were using USD earlier, can continue using that. The only difference is that previously it was mandatory for everyone to use USD everywhere because that was the only legal tender. Now those who want to go for an alternative do have a choice. So what the USD supporters want? They want to force everyone to stick with USD?