I have discovered that a lot of people refer to dinosaurs as being extinct animals that are only a thing of the past. I'd like to challenge that belief and I would invite any such person to come forward and defend their opinion that dinosaurs are indeed extinct.
This will be a short debate (2000 characters max for each argument) on a pretty simple topic, so we should finish this quite quickly.
Some species of dinosaurs still exist even today.
Species - a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial, e.g. Homo sapiens.
Dinosaurs - animals of the clade Dinosauria. It should be recognized that due to the massive variety of dinosaur species, the term would take a long time to describe fully, but here are a few examples of dinosaurs, so that you would get the idea of what I am talking about: Brachiosaurus altithorax, Triceratops horridus, Stegosaurus stenops etc.
Exist - (in this particular case) to be alive; to have living individuals.
Round 1: Acceptance only. No arguments allowed. Round 2: Constructive case by Pro. Constructive case by Con. Round 3: Rebuttals by Pro and Con. Round 4: Counter-rebuttals and summary by Pro and Con.
1. The resolution, definitions and structure stated above must be accepted unconditionally. 2. Any further definitions, if needed, shall be defined in a reasonable manner, using the most common meanings that apply to the given context. 3. No trolling, swearing or personal attacks. 4. No kritiks or semantics. 5. Please retain a friendly and civil atmosphere.
I will be arguing that there are modern dinosaur species and I accept the full burden of proof. My whole case will be based on showing that Birds (Aves), a class of animals with many currently living species, are dinosaurs. I will make use of this syllogism:
P1: All Animals of the Dinosauria clade are Dinosaurs P2: Birds belong to the Dinosauria clade C: Therefore, Birds are Dinosaurs
If P1 and P2 are true, then C necessarily follows from those two premises. P1 is true by definition (see Round 1), but P2 is not obvious and has to be shown to be true, using evidence.
Before I start, I feel the need to explain what a clade is, since I realized that I forgot to put the definition in Round 1:
Clade - A group of organisms believed to comprise all the evolutionary descendants of a common ancestor 
Thus, to show that Birds belong to the Dinosauria clade, I would have to show that birds share a common ancestor with other Dinosaurs. This can be done by demonstrating that Birds have sufficiently many anatomical similarities with other Dinosaurs. Not wasting too much space, I'll write out my main points, which I will expand on in further rounds.
A) Birds, like some other dinosaurs, have feathers and scales. 
B) Birds, like other dinosaurs, lay eggs.
C) Birds share major skeletal similarities with some dinosaurs, especially those from the Coelurosauria clade. 
D) The Archaeopteryx specimen is an example of a transitional fossil, showing a direct evolutionary lineage between non-Avian Reptiles and Modern Birds.  It has features of both Reptiles (e.g. teeth) and modern Birds (e.g. feathered wings)
Taken together, this evidence suggest that Birds are Dinosaurs.