Perhaps the person is pro-freedom to do what you want with your own life, but against making someone else die against their will?
Death penalty objections have several typical arguments behind them, including:
* Hypocricy: You’re punishing someone for killing, by killing them.
* Mistakes: Don’t want to kill innocent people, and the wrong people get convicted fairly often.
* Ineffectiveness: Studies indicate it doesn’t help discourage crime, and can actually increase it (e.g. it can make criminals more desperate to not be caught, causing them to victimize witnesses or make dangerous escape attempts, etc).
* Pacifism: Many people find killing to be plain morally unacceptable.
* Rehabilitation: Some killers can become good harmless people.
In short, for many people, there are objections to the death penalty, and they have little or nothing to do with suicide, for many people.
The question seems to think assisted suicide tends to involve tricking or manipulating people who don’t want to die, to be killed. I don’t think many people who are in favor of assisted suicide are for that. For those that are, I tend to imagine they’re either more interested in the profit margins of insurance companies or hospital corporations.