...which responding to them surely does?
Because you think you are winning the debate they initiated, and that debate will continue until the ads stop running (not when the chattering classes grow tired of them). So you want your counter-argument in the news as well for as much of that time-frame as possible. At this point I think the Libs would like to keep these various CPoC attacks center-stage as long as they can; the ads provide a nice contrast with what Ignatieff is up to these days.
By the way, aesthetic merits aside, what is the point of a website like Ignatieff.me? Is anyone but the hardest of hardcore poli-junkies going to ever visit it more than once? Unless you're going to run a continual stream of updates, it essentially becomes a one-off gag. And the official party website exists for that kind of thing (updates, not gags).
This isn't just a Conservative fault. It seems parties are continually launching static web-pages that nobody is likely to visit a 2nd time. I don't see the point to it.