Your goal to present your material in as unbiased a way as possible is very admirable! There's lots of bloggers out there who aren't interested in having ads on their site, for reasons of design or principle. But if this issue is this important to you, you'll have to keep it in mind when you use free services from third parties like WordPress.com to host your content.
You do have that option to buy the No-Ads Upgrade, as you mentioned you intended to do. It's a great option and still gives you, as macmanx mentioned, all of the professional backend support, gorgeous themes, and technical assistance that comes with keeping your content at WordPress.com.
The free ads that WordPress.com occasionally places on some sites are not "luring" readers to commercial content. Nobody has to click on an ad, and WordPress.com users are told about the advertising policy when they sign up for a blog and the Terms of Service are presented. When a user clicks "agree" it's a signal that they're ok with this advertising.
Have you ever considered self-hosting your own installation of WordPress.org? If this level of freedom from any outside interest is something that's this important to you, paying for your own hosting and installing your own version of WordPress would give you 100% control over all aspects of your blog.