The AI rarely purposefully tries to thwart your victory condition.
Diplomatic Victory, while too easy, is probably the Victory condition that the AI defends the best as every AI Civ will nominate you to lose two points every WC passed a certain DV point threshold. It's essentially impossible to counter other than to cheese the system and vote for your to lose 2 points to at least salvage 1 point and try to guess correctly on the remaining two.
For Culture Victory, there are some built in AI safeguards. The AI will actively use the Music Censorship card quite actively if they have it, barring your Rock Bands from their lands. This is quite an effective hard counter.
The AI will also stop selling you any more Great Works if it determines that you are close enough to a Culture Victory.
The AI doesn't have any specific defenses against Domination Victory because they build too few units and manage the ones they manage to produce horribly.
I can't think of any specific counters the AI uses against Science Victory other than competing in the Space Race itself.
I don’t think I've ever had an AI Disrupt my Spaceport ever, even though I leave it undefended half the time.
I did lose a Deity Space Race game to Montezuma the other day because he actually built Lagrange Laser Stations immediately after launching his Exoplanet Expedition, which I was surprised to see.
I also don't think the AI has any specific strategies to counter Religious Victories either, though they do seem quite adept at getting their Religious Combat strength up to high levels via Diplomatic visibility and other government/policy options.