I have said it frequently enough when people ask about down votes: By philosophy and design votes are anonymous and neither voting up nor voting down requires any mandatory explanation.
The tooltip that appears when your mouse pointer hoovers over the down button next to an answer states: "This answer is not useful", which is short, to the point and of course quite subjective.
The manual explains a bit more:
When should I vote down?
Use your downvotes whenever you encounter an egregiously sloppy, no-effort-expended post, or an answer that is clearly and perhaps dangerously incorrect.
You have a limited number of votes per day, and answer down-votes cost you a tiny bit of reputation on top of that; use them wisely.
In addition we don't like spam, link-only answers or answers that consist of just code/screenshots/command lines without supporting text.
Other than the above we don't have a policy on voting certain types of answers, but "crappy questions attract crappy answers" and the down votes for the both of them can go hand-in-hand.
Is it bad practise to answer questions that do not comply with the sites rules?
IMHO it is great that you are willing to share your knowledge and experience and you can answer and/or comment whatever question you feel is worth to expend the energy on.
But from the perspective of maintaining a healthy community/site rewarding "bad behaviour" is not constructive.
Your own answer already shows some of that struggle as well, you explain you don't want to outright recommend certain products and end up recommending the OP to use a search engine with certain keywords instead. Which, technically speaking, does not actually answer the question...
