Edit: Jesus Christ, people. If you buy a $150 Thinkpad made by slave labor instead of a $1,200 MacBook made by slave labor, you're still supporting a capitalist economy based on slave labor. We all do. We have no choice. The number of smug liberals in the comments saying "well I buy a cheap used laptop" or "well I buy coffee beans and make my own coffee" are completely missing the fucking point.
Don't tell yourself your consumption is moral. All of us make unethical choices every day because there is no ethical consumption under capitalism. Accept your shame and guilt and let it drive you to do better.
Buying a used Thinkpad doesn't change the fact that it was made by slave labor. It might make you feel better to buy one, but it changes absolutely nothing. You still bought an item made in part by slaves or near-slaves. And you're keeping the market alive for that to continue.